diff --git a/poetry.lock b/poetry.lock
index cefa2c6..9a2e23b 100644
--- a/poetry.lock
+++ b/poetry.lock
@@ -1,9 +1,10 @@
-# This file is automatically @generated by Poetry 1.5.1 and should not be changed by hand.
+# This file is automatically @generated by Poetry 1.4.2 and should not be changed by hand.
 
 [[package]]
 name = "astroid"
 version = "2.11.7"
 description = "An abstract syntax tree for Python with inference support."
+category = "dev"
 optional = false
 python-versions = ">=3.6.2"
 files = [
@@ -22,6 +23,7 @@ wrapt = ">=1.11,<2"
 name = "colorama"
 version = "0.4.6"
 description = "Cross-platform colored terminal text."
+category = "dev"
 optional = false
 python-versions = "!=3.0.*,!=3.1.*,!=3.2.*,!=3.3.*,!=3.4.*,!=3.5.*,!=3.6.*,>=2.7"
 files = [
@@ -33,6 +35,7 @@ files = [
 name = "coverage"
 version = "7.2.7"
 description = "Code coverage measurement for Python"
+category = "dev"
 optional = false
 python-versions = ">=3.7"
 files = [
@@ -105,6 +108,7 @@ toml = ["tomli"]
 name = "dill"
 version = "0.3.6"
 description = "serialize all of python"
+category = "dev"
 optional = false
 python-versions = ">=3.7"
 files = [
@@ -119,6 +123,7 @@ graph = ["objgraph (>=1.7.2)"]
 name = "isort"
 version = "5.11.5"
 description = "A Python utility / library to sort Python imports."
+category = "dev"
 optional = false
 python-versions = ">=3.7.0"
 files = [
@@ -136,6 +141,7 @@ requirements-deprecated-finder = ["pip-api", "pipreqs"]
 name = "joblib"
 version = "1.2.0"
 description = "Lightweight pipelining with Python functions"
+category = "main"
 optional = false
 python-versions = ">=3.7"
 files = [
@@ -147,6 +153,7 @@ files = [
 name = "lazy-object-proxy"
 version = "1.9.0"
 description = "A fast and thorough lazy object proxy."
+category = "dev"
 optional = false
 python-versions = ">=3.7"
 files = [
@@ -192,6 +199,7 @@ files = [
 name = "mccabe"
 version = "0.7.0"
 description = "McCabe checker, plugin for flake8"
+category = "dev"
 optional = false
 python-versions = ">=3.6"
 files = [
@@ -199,21 +207,11 @@ files = [
     {file = "mccabe-0.7.0.tar.gz", hash = "sha256:348e0240c33b60bbdf4e523192ef919f28cb2c3d7d5c7794f74009290f236325"},
 ]
 
-[[package]]
-name = "optional-py"
-version = "1.3.2"
-description = "An implementation of the Optional object in Python"
-optional = false
-python-versions = ">=2.7, !=3.0.*, !=3.1.*, !=3.2.*, !=3.3.*, !=3.4.*"
-files = [
-    {file = "optional.py-1.3.2-py2.py3-none-any.whl", hash = "sha256:41b575c96377b6f8fedc4aef0d0bcc172bbf7f143089f149dc2b4c0812fe2984"},
-    {file = "optional.py-1.3.2.tar.gz", hash = "sha256:e0040b29d8e671245b92fffe3abc5aa3bd8870e9a804d7ac7ad377a370cccadc"},
-]
-
 [[package]]
 name = "parameterized"
 version = "0.9.0"
 description = "Parameterized testing with any Python test framework"
+category = "dev"
 optional = false
 python-versions = ">=3.7"
 files = [
@@ -226,26 +224,28 @@ dev = ["jinja2"]
 
 [[package]]
 name = "platformdirs"
-version = "3.5.1"
+version = "3.8.0"
 description = "A small Python package for determining appropriate platform-specific dirs, e.g. a \"user data dir\"."
+category = "dev"
 optional = false
 python-versions = ">=3.7"
 files = [
-    {file = "platformdirs-3.5.1-py3-none-any.whl", hash = "sha256:e2378146f1964972c03c085bb5662ae80b2b8c06226c54b2ff4aa9483e8a13a5"},
-    {file = "platformdirs-3.5.1.tar.gz", hash = "sha256:412dae91f52a6f84830f39a8078cecd0e866cb72294a5c66808e74d5e88d251f"},
+    {file = "platformdirs-3.8.0-py3-none-any.whl", hash = "sha256:ca9ed98ce73076ba72e092b23d3c93ea6c4e186b3f1c3dad6edd98ff6ffcca2e"},
+    {file = "platformdirs-3.8.0.tar.gz", hash = "sha256:b0cabcb11063d21a0b261d557acb0a9d2126350e63b70cdf7db6347baea456dc"},
 ]
 
 [package.dependencies]
-typing-extensions = {version = ">=4.5", markers = "python_version < \"3.8\""}
+typing-extensions = {version = ">=4.6.3", markers = "python_version < \"3.8\""}
 
 [package.extras]
-docs = ["furo (>=2023.3.27)", "proselint (>=0.13)", "sphinx (>=6.2.1)", "sphinx-autodoc-typehints (>=1.23,!=1.23.4)"]
-test = ["appdirs (==1.4.4)", "covdefaults (>=2.3)", "pytest (>=7.3.1)", "pytest-cov (>=4)", "pytest-mock (>=3.10)"]
+docs = ["furo (>=2023.5.20)", "proselint (>=0.13)", "sphinx (>=7.0.1)", "sphinx-autodoc-typehints (>=1.23,!=1.23.4)"]
+test = ["appdirs (==1.4.4)", "covdefaults (>=2.3)", "pytest (>=7.3.1)", "pytest-cov (>=4.1)", "pytest-mock (>=3.10)"]
 
 [[package]]
 name = "pylint"
 version = "2.13.9"
 description = "python code static checker"
+category = "dev"
 optional = false
 python-versions = ">=3.6.2"
 files = [
@@ -268,13 +268,14 @@ testutil = ["gitpython (>3)"]
 
 [[package]]
 name = "setuptools"
-version = "67.8.0"
+version = "68.0.0"
 description = "Easily download, build, install, upgrade, and uninstall Python packages"
+category = "dev"
 optional = false
 python-versions = ">=3.7"
 files = [
-    {file = "setuptools-67.8.0-py3-none-any.whl", hash = "sha256:5df61bf30bb10c6f756eb19e7c9f3b473051f48db77fddbe06ff2ca307df9a6f"},
-    {file = "setuptools-67.8.0.tar.gz", hash = "sha256:62642358adc77ffa87233bc4d2354c4b2682d214048f500964dbe760ccedf102"},
+    {file = "setuptools-68.0.0-py3-none-any.whl", hash = "sha256:11e52c67415a381d10d6b462ced9cfb97066179f0e871399e006c4ab101fc85f"},
+    {file = "setuptools-68.0.0.tar.gz", hash = "sha256:baf1fdb41c6da4cd2eae722e135500da913332ab3f2f5c7d33af9b492acb5235"},
 ]
 
 [package.extras]
@@ -286,6 +287,7 @@ testing-integration = ["build[virtualenv]", "filelock (>=3.4.0)", "jaraco.envs (
 name = "tomli"
 version = "2.0.1"
 description = "A lil' TOML parser"
+category = "dev"
 optional = false
 python-versions = ">=3.7"
 files = [
@@ -297,6 +299,7 @@ files = [
 name = "typed-ast"
 version = "1.5.4"
 description = "a fork of Python 2 and 3 ast modules with type comment support"
+category = "dev"
 optional = false
 python-versions = ">=3.6"
 files = [
@@ -328,19 +331,21 @@ files = [
 
 [[package]]
 name = "typing-extensions"
-version = "4.6.1"
+version = "4.6.3"
 description = "Backported and Experimental Type Hints for Python 3.7+"
+category = "dev"
 optional = false
 python-versions = ">=3.7"
 files = [
-    {file = "typing_extensions-4.6.1-py3-none-any.whl", hash = "sha256:6bac751f4789b135c43228e72de18637e9a6c29d12777023a703fd1a6858469f"},
-    {file = "typing_extensions-4.6.1.tar.gz", hash = "sha256:558bc0c4145f01e6405f4a5fdbd82050bd221b119f4bf72a961a1cfd471349d6"},
+    {file = "typing_extensions-4.6.3-py3-none-any.whl", hash = "sha256:88a4153d8505aabbb4e13aacb7c486c2b4a33ca3b3f807914a9b4c844c471c26"},
+    {file = "typing_extensions-4.6.3.tar.gz", hash = "sha256:d91d5919357fe7f681a9f2b5b4cb2a5f1ef0a1e9f59c4d8ff0d3491e05c0ffd5"},
 ]
 
 [[package]]
 name = "wrapt"
 version = "1.15.0"
 description = "Module for decorators, wrappers and monkey patching."
+category = "dev"
 optional = false
 python-versions = "!=3.0.*,!=3.1.*,!=3.2.*,!=3.3.*,!=3.4.*,>=2.7"
 files = [
@@ -424,4 +429,4 @@ files = [
 [metadata]
 lock-version = "2.0"
 python-versions = ">=3.7,<4.0"
-content-hash = "bc19628cf2f534e9ce2bb75506ce23bb5add8a3203605b5542384e49f7ab9df0"
+content-hash = "cd51f0d06664ffbb0492e2ea1fa9c88eaf558d7c7d5ef10827ee15ecb56bbb9f"
diff --git a/pyproject.toml b/pyproject.toml
index 74af2f0..ec3bcf7 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -15,7 +15,6 @@ packages = [
 [tool.poetry.dependencies]
 python = ">=3.7,<4.0"
 joblib = "~1.2.0"
-optional-py = "^1.3.2"
 
 [tool.poetry.group.test.dependencies]
 parameterized = "*"
diff --git a/pystreamapi/__optional.py b/pystreamapi/__optional.py
new file mode 100644
index 0000000..0032d3f
--- /dev/null
+++ b/pystreamapi/__optional.py
@@ -0,0 +1,114 @@
+class Optional:
+    """
+    A container object which may or may not contain a non-none value.
+
+    If a value is present, `is_present()` will return `True` and `get()` will return the value.
+    If a value is not present, `is_present()` will return `False`
+    and `get()` will raise a `ValueError`.
+    Additional methods provide ways to handle the presence or absence of a contained value.
+
+    This class is inspired by Java's `Optional` class.
+    """
+
+    def __init__(self, value=None):
+        """
+        Constructs an Optional with the given value.
+
+        If the value is None, the Optional is considered empty.
+        """
+        self._value = value
+        self._is_present = value is not None
+
+    @staticmethod
+    def of(value):
+        """
+        Returns an Optional with the given non-none value.
+
+        Raises a ValueError if the value is None.
+        """
+        if value is None:
+            raise ValueError("Value cannot be None")
+        return Optional(value)
+
+    @staticmethod
+    def empty():
+        """Returns an empty Optional."""
+        return Optional()
+
+    def is_present(self):
+        """Returns `True` if the Optional contains a non-none value, `False` otherwise."""
+        return self._is_present
+
+    def get(self):
+        """Returns the value if present, otherwise raises a `ValueError`."""
+        if not self._is_present:
+            raise ValueError("Value is not present")
+        return self._value
+
+    def or_else(self, default_value):
+        """Returns the value if present, otherwise returns the given default value."""
+        return self._value if self._is_present else default_value
+
+    def or_else_get(self, supplier):
+        """
+        Returns the value if present, otherwise calls the given supplier function to get a
+        default value.
+        """
+        return self._value if self._is_present else supplier()
+
+    def map(self, mapper):
+        """
+        Applies the given mapper function to the value if present, returning a new Optional
+        with the result.
+
+        If the Optional is empty, returns an empty Optional.
+        """
+        if not self._is_present:
+            return Optional()
+        mapped_value = mapper(self._value)
+        return Optional(mapped_value)
+
+    def flat_map(self, mapper):
+        """
+        Applies the given mapper function to the value if present, returning the result.
+
+        If the Optional is empty, returns an empty Optional.
+        If the mapper function does not return an Optional, raises a TypeError.
+        """
+        if not self._is_present:
+            return Optional()
+        optional_result = mapper(self._value)
+        if not isinstance(optional_result, Optional):
+            raise TypeError("Mapper function must return an Optional")
+        return optional_result
+
+    def filter(self, predicate):
+        """
+        Returns an Optional containing the value if present and the predicate is true,
+        otherwise an empty Optional.
+        """
+        return self if self._is_present and predicate(self._value) else Optional()
+
+    def if_present(self, consumer):
+        """Calls the given consumer function with the value if present, otherwise does nothing."""
+        if self._is_present:
+            consumer(self._value)
+
+    def __str__(self):
+        """Returns a string representation of the Optional."""
+        return f"Optional({self._value if self._is_present else ''})"
+
+    def __repr__(self):
+        """Returns a string representation of the Optional."""
+        return self.__str__()
+
+    def __eq__(self, other):
+        """
+        Returns `True` if the other object is an Optional with the same value,
+        `False` otherwise.
+        """
+        return self._value == other._value if isinstance(other, Optional) else False
+
+    def __hash__(self):
+        """Returns the hash of the Optional's value."""
+        return hash(self._value)
diff --git a/pystreamapi/_streams/__base_stream.py b/pystreamapi/_streams/__base_stream.py
index 78a6595..9a7df55 100644
--- a/pystreamapi/_streams/__base_stream.py
+++ b/pystreamapi/_streams/__base_stream.py
@@ -2,14 +2,11 @@
 from abc import abstractmethod
 from builtins import reversed
 from functools import cmp_to_key
-from typing import Iterable, Callable, Any, TypeVar, Iterator, Union
-
-from optional import Optional
-from optional.nothing import Nothing
-from optional.something import Something
+from typing import Iterable, Callable, Any, TypeVar, Iterator
 
 from pystreamapi._lazy.process import Process
 from pystreamapi._lazy.queue import ProcessQueue
+from pystreamapi.__optional import Optional
 
 K = TypeVar('K')
 _V = TypeVar('_V')
@@ -320,7 +317,7 @@ def max(self):
 
     @abstractmethod
     def reduce(self, predicate: Callable[[K, K], K], identity=_identity_missing,
-               depends_on_state=False) -> Union[K, Something, Nothing]:
+               depends_on_state=False) -> Optional:
         """
         Performs a reduction on the elements of this stream, using the provided identity value
         and an associative accumulation function, and returns the reduced value.
diff --git a/pystreamapi/_streams/__parallel_stream.py b/pystreamapi/_streams/__parallel_stream.py
index 1b4d0aa..91099ef 100644
--- a/pystreamapi/_streams/__parallel_stream.py
+++ b/pystreamapi/_streams/__parallel_stream.py
@@ -2,7 +2,7 @@
 from typing import Callable, Any, Iterable
 
 from joblib import Parallel, delayed
-from optional import Optional
+from pystreamapi.__optional import Optional
 
 import pystreamapi._streams.__base_stream as stream
 from pystreamapi._parallel.fork_and_join import Parallelizer
@@ -15,7 +15,7 @@ class ParallelStream(stream.BaseStream):
 
     def __init__(self, source: Iterable[stream.K]):
         super().__init__(source)
-        self.parallelizer = Parallelizer()
+        self._parallelizer = Parallelizer()
 
     def all_match(self, predicate: Callable[[Any], bool]):
         self._trigger_exec()
@@ -24,7 +24,7 @@ def all_match(self, predicate: Callable[[Any], bool]):
 
     def _filter(self, predicate: Callable[[Any], bool]):
         self._set_parallelizer_src()
-        self._source = self.parallelizer.filter(predicate)
+        self._source = self._parallelizer.filter(predicate)
 
     def find_any(self):
         self._trigger_exec()
@@ -77,11 +77,11 @@ def reduce(self, predicate: Callable[[Any, Any], Any], identity=_identity_missin
         return identity if identity is not _identity_missing else Optional.empty()
 
     def __reduce(self, pred, _):
-        return self.parallelizer.reduce(pred)
+        return self._parallelizer.reduce(pred)
 
     def to_dict(self, key_mapper: Callable[[Any], Any]) -> dict:
         self._trigger_exec()
         return dict(self._group_to_dict(key_mapper))
 
     def _set_parallelizer_src(self):
-        self.parallelizer.set_source(self._source)
+        self._parallelizer.set_source(self._source)
diff --git a/pystreamapi/_streams/__sequential_stream.py b/pystreamapi/_streams/__sequential_stream.py
index f49026b..099ba18 100644
--- a/pystreamapi/_streams/__sequential_stream.py
+++ b/pystreamapi/_streams/__sequential_stream.py
@@ -1,7 +1,7 @@
 from functools import reduce
 from typing import Callable, Any
 
-from optional import Optional
+from pystreamapi.__optional import Optional
 
 import pystreamapi._streams.__base_stream as stream
 
diff --git a/pystreamapi/_streams/numeric/__parallel_numeric_stream.py b/pystreamapi/_streams/numeric/__parallel_numeric_stream.py
index d8f2c2f..b54ecdd 100644
--- a/pystreamapi/_streams/numeric/__parallel_numeric_stream.py
+++ b/pystreamapi/_streams/numeric/__parallel_numeric_stream.py
@@ -21,4 +21,4 @@ def sum(self) -> Union[float, int, None]:
     def __sum(self):
         """Parallel sum method"""
         self._set_parallelizer_src()
-        return self.parallelizer.reduce(lambda x, y: x + y)
+        return self._parallelizer.reduce(lambda x, y: x + y)
diff --git a/tests/test_base_stream.py b/tests/test_base_stream.py
index 60ee144..35fc2de 100644
--- a/tests/test_base_stream.py
+++ b/tests/test_base_stream.py
@@ -1,6 +1,6 @@
 import unittest
 
-from optional import Optional
+from pystreamapi.__optional import Optional
 
 from pystreamapi.__stream import Stream
 from pystreamapi._streams.__parallel_stream import ParallelStream
diff --git a/tests/test_optional.py b/tests/test_optional.py
new file mode 100644
index 0000000..0112f3c
--- /dev/null
+++ b/tests/test_optional.py
@@ -0,0 +1,143 @@
+import unittest
+from pystreamapi.__optional import Optional
+
+class TestOptional(unittest.TestCase):
+    def test_of(self):
+        # Test that creating an Optional with a non-None value works
+        optional = Optional.of(5)
+        self.assertTrue(optional.is_present())
+        self.assertEqual(optional.get(), 5)
+
+        # Test that creating an Optional with None raises a ValueError
+        with self.assertRaises(ValueError):
+            Optional.of(None)
+
+    def test_empty(self):
+        # Test that creating an empty Optional works
+        optional = Optional.empty()
+        self.assertFalse(optional.is_present())
+
+    def test_get(self):
+        # Test that get returns the Optional's value if present
+        optional = Optional.of(5)
+        self.assertEqual(optional.get(), 5)
+
+        # Test that get raises a ValueError if the Optional is empty
+        optional = Optional.empty()
+        with self.assertRaises(ValueError):
+            optional.get()
+
+    def test_or_else(self):
+        # Test that or_else returns the Optional's value if present
+        optional = Optional.of(5)
+        self.assertEqual(optional.or_else(10), 5)
+
+        # Test that or_else returns the default value if the Optional is empty
+        optional = Optional.empty()
+        self.assertEqual(optional.or_else(10), 10)
+
+    def test_or_else_get(self):
+        # Test that or_else_get returns the Optional's value if present
+        optional = Optional.of(5)
+        self.assertEqual(optional.or_else_get(lambda: 10), 5)
+
+        # Test that or_else_get returns the supplier's value if the Optional is empty
+        optional = Optional.empty()
+        self.assertEqual(optional.or_else_get(lambda: 10), 10)
+
+    def test_map(self):
+        # Test that map applies the mapper function to the Optional's value
+        optional = Optional.of(5)
+        mapped_optional = optional.map(lambda x: x * 2)
+        self.assertTrue(mapped_optional.is_present())
+        self.assertEqual(mapped_optional.get(), 10)
+
+        # Test that map returns an empty Optional if the original Optional is empty
+        optional = Optional.empty()
+        mapped_optional = optional.map(lambda x: x * 2)
+        self.assertFalse(mapped_optional.is_present())
+
+    def test_flat_map(self):
+        # Test that flat_map applies the mapper function to the
+        # Optional's value and returns the result
+        optional = Optional.of(5)
+        mapped_optional = optional.flat_map(lambda x: Optional.of(x * 2))
+        self.assertTrue(mapped_optional.is_present())
+        self.assertEqual(mapped_optional.get(), 10)
+
+        # Test that flat_map returns an empty Optional if the original Optional is empty
+        optional = Optional.empty()
+        mapped_optional = optional.flat_map(lambda x: Optional.of(x * 2))
+        self.assertFalse(mapped_optional.is_present())
+
+        # Test that flat_map raises a TypeError if the mapper function doesn't return an Optional
+        optional = Optional.of(5)
+        with self.assertRaises(TypeError):
+            optional.flat_map(lambda x: x * 2)
+
+    def test_filter(self):
+        # Test that filter returns the Optional if the predicate is true
+        optional = Optional.of(5)
+        filtered_optional = optional.filter(lambda x: x > 3)
+        self.assertTrue(filtered_optional.is_present())
+        self.assertEqual(filtered_optional.get(), 5)
+
+        # Test that filter returns an empty Optional if the predicate is false
+        optional = Optional.of(5)
+        filtered_optional = optional.filter(lambda x: x > 10)
+        self.assertFalse(filtered_optional.is_present())
+
+        # Test that filter returns an empty Optional if the original Optional is empty
+        optional = Optional.empty()
+        filtered_optional = optional.filter(lambda x: x > 3)
+        self.assertFalse(filtered_optional.is_present())
+
+    def test_if_present(self):
+        # Test that if_present calls the consumer function if the Optional is present
+        optional = Optional.of(5)
+        result = []
+        optional.if_present(result.append)
+        self.assertEqual(result, [5])
+
+        # Test that if_present doesn't call the consumer function if the Optional is empty
+        optional = Optional.empty()
+        result = []
+        optional.if_present(result.append)
+        self.assertEqual(result, [])
+
+    def test_str(self):
+        # Test that str returns the string representation of the Optional's value
+        optional = Optional.of(5)
+        self.assertEqual(str(optional), "Optional(5)")
+
+        # Test that str returns "Optional()" if the Optional is empty
+        optional = Optional.empty()
+        self.assertEqual(str(optional), "Optional()")
+
+    def test_repr(self):
+        # Test that repr returns the string representation of the Optional's value
+        optional = Optional.of(5)
+        self.assertEqual(repr(optional), "Optional(5)")
+
+        # Test that repr returns "Optional()" if the Optional is empty
+        optional = Optional.empty()
+        self.assertEqual(repr(optional), "Optional()")
+
+    def test_eq(self):
+        # Test that eq returns True if the two Optionals have the same value
+        optional1 = Optional.of(5)
+        optional2 = Optional.of(5)
+        self.assertEqual(optional1, optional2)
+
+        # Test that eq returns False if the two Optionals have different values
+        optional1 = Optional.of(5)
+        optional2 = Optional.of(10)
+        self.assertNotEqual(optional1, optional2)
+
+        # Test that eq returns False if the other object is not an Optional
+        optional = Optional.of(5)
+        self.assertNotEqual(optional, 5)
+
+    def test_hash(self):
+        optional = Optional(5)
+        self.assertEqual(hash(5), hash(optional))
diff --git a/tests/test_stream_implementation.py b/tests/test_stream_implementation.py
index 006a124..9326954 100644
--- a/tests/test_stream_implementation.py
+++ b/tests/test_stream_implementation.py
@@ -1,13 +1,12 @@
 import unittest
 
-from optional import Optional
-from optional.something import Something
 from parameterized import parameterized_class
 
 from pystreamapi._streams.__base_stream import BaseStream
 from pystreamapi._streams.__parallel_stream import ParallelStream
 from pystreamapi._streams.__sequential_stream import SequentialStream
 from pystreamapi._streams.numeric.__sequential_numeric_stream import SequentialNumericStream
+from pystreamapi.__optional import Optional
 
 
 @parameterized_class("stream", [
@@ -104,8 +103,7 @@ def test_limit_empty(self):
     def test_reduce_no_identity(self):
         src = [1, 2, 3, 4, 5]
         result = self.stream(src).reduce(lambda x, y: x + y)
-        self.assertEqual(type(result), Something)
-        self.assertEqual(result.get_or_default("Empty"), sum(src))
+        self.assertEqual(result.or_else("Empty"), sum(src))
 
     def test_reduce_with_identity(self):
         src = [1, 2, 3, 4, 5]
@@ -116,7 +114,6 @@ def test_reduce_with_identity(self):
     def test_reduce_depends_on_state(self):
         src = [4, 3, 2, 1]
         result = self.stream(src).reduce(lambda x, y: x - y, depends_on_state=True)
-        self.assertEqual(type(result), Something)
         self.assertEqual(result.get(), -2)
 
     def test_reduce_empty_stream_no_identity(self):