Python: Refactoring. Use get_function and get_plugin. (microsoft#6382)

### Motivation and Context

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Refactoring some of the code following [this
advice](microsoft#6371 (comment))
from the maintainers.

### Description

<!-- Describe your changes, the overall approach, the underlying design.
These notes will help understanding how your code works. Thanks! -->

Look up kernel functions and plugins with the `get_function` and
`get_plugin` method. Removed the unused `DEFAULT_CHAT_SYSTEM_PROMPT`

### Contribution Checklist

<!-- Before submitting this PR, please make sure: -->

- [x] The code builds clean without any errors or warnings
- [x] The PR follows the [SK Contribution
Guidelines](https://github.com/microsoft/semantic-kernel/blob/main/CONTRIBUTING.md)
and the [pre-submission formatting
script](https://github.com/microsoft/semantic-kernel/blob/main/CONTRIBUTING.md#development-scripts)
raises no violations
- [x] All unit tests pass, and I have added new tests where possible
- [x] I didn't break anyone 😄

---------

Co-authored-by: Evan Mattson <35585003+moonbox3@users.noreply.github.com>

Author: stefan521

python/samples/concepts/search/bing_plugin_examples.py

@@ -14,7 +14,7 @@ async def example1(kernel: Kernel, search_plugin_name: str):
     print("======== Bing and Google Search Plugins ========")
 
     question = "What's the largest building in the world?"
-    function = kernel.plugins[search_plugin_name]["search"]
+    function = kernel.get_function(plugin_name=search_plugin_name, function_name="search")
     result = await kernel.invoke(function, query=question)
 
     print(question)

python/samples/learn_resources/serializing_prompts.py

@@ -50,7 +50,9 @@ async def main():
         plugin_name="ConversationSummaryPlugin",
     )
 
-    summarize_function = kernel.plugins["ConversationSummaryPlugin"]["SummarizeConversation"]
+    summarize_function = kernel.get_function(
+        plugin_name="ConversationSummaryPlugin", function_name="SummarizeConversation"
+    )
 
     # Create the history
     history = ChatHistory()

python/semantic_kernel/connectors/ai/open_ai/const.py

@@ -4,4 +4,3 @@
 
 DEFAULT_AZURE_API_VERSION: Final[str] = "2024-02-01"
 USER_AGENT: Final[str] = "User-Agent"
-DEFAULT_CHAT_SYSTEM_PROMPT: Final[str] = "Assistant is a large language model."

python/tests/unit/core_plugins/test_http_plugin.py

@@ -21,10 +21,10 @@ async def test_it_can_be_imported():
     kernel = Kernel()
     plugin = HttpPlugin()
     kernel.add_plugin(plugin, "http")
-    assert kernel.plugins["http"] is not None
-    assert kernel.plugins["http"].name == "http"
-    assert kernel.plugins["http"]["getAsync"] is not None
-    assert kernel.plugins["http"]["postAsync"] is not None
+    assert kernel.get_plugin(plugin_name="http") is not None
+    assert kernel.get_plugin(plugin_name="http").name == "http"
+    assert kernel.get_function(plugin_name="http", function_name="getAsync") is not None
+    assert kernel.get_function(plugin_name="http", function_name="postAsync") is not None
 
 
 @patch("aiohttp.ClientSession.get")

python/tests/unit/core_plugins/test_math_plugin.py

@@ -15,10 +15,10 @@ def test_can_be_instantiated():
 def test_can_be_imported():
     kernel = Kernel()
     kernel.add_plugin(MathPlugin(), "math")
-    assert kernel.plugins["math"] is not None
-    assert kernel.plugins["math"].name == "math"
-    assert kernel.plugins["math"]["Add"] is not None
-    assert kernel.plugins["math"]["Subtract"] is not None
+    assert kernel.get_plugin(plugin_name="math") is not None
+    assert kernel.get_plugin(plugin_name="math").name == "math"
+    assert kernel.get_function(plugin_name="math", function_name="Add") is not None
+    assert kernel.get_function(plugin_name="math", function_name="Subtract") is not None
 
 
 @pytest.mark.parametrize(

python/tests/unit/core_plugins/test_sessions_python_plugin.py

@@ -30,8 +30,8 @@ def test_validate_endpoint(aca_python_sessions_unit_test_env):
 def test_it_can_be_imported(kernel: Kernel, aca_python_sessions_unit_test_env):
     plugin = SessionsPythonTool(auth_callback=test_auth_callback)
     assert kernel.add_plugin(plugin=plugin, plugin_name="PythonCodeInterpreter")
-    assert kernel.plugins["PythonCodeInterpreter"] is not None
-    assert kernel.plugins["PythonCodeInterpreter"].name == "PythonCodeInterpreter"
+    assert kernel.get_plugin(plugin_name="PythonCodeInterpreter") is not None
+    assert kernel.get_plugin(plugin_name="PythonCodeInterpreter").name == "PythonCodeInterpreter"
 
 
 @pytest.mark.asyncio

python/tests/unit/core_plugins/test_text_memory_plugin.py

@@ -36,7 +36,7 @@ def test_can_be_instantiated(memory: SemanticTextMemory):
 
 def test_can_be_imported(kernel: Kernel, memory: SemanticTextMemory):
     kernel.add_plugin(TextMemoryPlugin(memory), "memory_plugin")
-    assert not kernel.plugins["memory_plugin"]["recall"].is_prompt
+    assert not kernel.get_function(plugin_name="memory_plugin", function_name="recall").is_prompt
 
 
 @mark.asyncio

python/tests/unit/core_plugins/test_text_plugin.py

@@ -10,12 +10,12 @@ def test_can_be_instantiated():
 
 def test_can_be_imported(kernel: Kernel):
     kernel.add_plugin(TextPlugin(), "text_plugin")
-    assert not kernel.plugins["text_plugin"]["trim"].is_prompt
+    assert not kernel.get_function(plugin_name="text_plugin", function_name="trim").is_prompt
 
 
 def test_can_be_imported_with_name(kernel: Kernel):
     kernel.add_plugin(TextPlugin(), "text")
-    assert not kernel.plugins["text"]["trim"].is_prompt
+    assert not kernel.get_function(plugin_name="text", function_name="trim").is_prompt
 
 
 def test_can_trim():

python/tests/unit/core_plugins/test_time_plugin.py

@@ -15,9 +15,9 @@ def test_can_be_instantiated():
 def test_can_be_imported():
     kernel = sk.Kernel()
     kernel.add_plugin(TimePlugin(), "time")
-    assert kernel.plugins["time"] is not None
-    assert kernel.plugins["time"].name == "time"
-    assert kernel.plugins["time"]["now"] is not None
+    assert kernel.get_plugin(plugin_name="time") is not None
+    assert kernel.get_plugin(plugin_name="time").name == "time"
+    assert kernel.get_function(plugin_name="time", function_name="now") is not None
 
 
 def test_date():

python/tests/unit/kernel/test_kernel.py

@@ -279,7 +279,7 @@ async def test_add_plugin_from_openai(mock_parse_openai_manifest, kernel: Kernel
             enable_dynamic_payload=True,
         ),
     )
-    plugin = kernel.plugins["TestOpenAIPlugin"]
+    plugin = kernel.get_plugin(plugin_name="TestOpenAIPlugin")
     assert plugin is not None
     assert plugin.name == "TestOpenAIPlugin"
     assert plugin.functions.get("GetSecret") is not None
@@ -295,7 +295,7 @@ def test_import_plugin_from_openapi(kernel: Kernel):
         plugin_name="TestOpenAPIPlugin",
         openapi_document_path=openapi_spec_file,
     )
-    plugin = kernel.plugins["TestOpenAPIPlugin"]
+    plugin = kernel.get_plugin(plugin_name="TestOpenAPIPlugin")
     assert plugin is not None
     assert plugin.name == "TestOpenAPIPlugin"
     assert plugin.functions.get("GetSecret") is not None

python/tests/unit/kernel/test_register_functions.py

@@ -14,11 +14,11 @@
 
 @pytest.mark.asyncio
 async def test_register_valid_native_function(kernel: Kernel, decorated_native_function: Callable):
-    kernel.add_function("TestPlugin", function=decorated_native_function)
-    registered_func = kernel.get_function("TestPlugin", "getLightStatus")
+    kernel.add_function(plugin_name="TestPlugin", function=decorated_native_function)
+    registered_func = kernel.get_function(plugin_name="TestPlugin", function_name="getLightStatus")
 
     assert isinstance(registered_func, KernelFunction)
-    assert kernel.plugins["TestPlugin"]["getLightStatus"] == registered_func
+    assert kernel.get_function(plugin_name="TestPlugin", function_name="getLightStatus") == registered_func
     func_result = await registered_func.invoke(kernel, KernelArguments(arg1="testtest"))
     assert str(func_result) == "test"