Add model module and tests

model.Object is the dict with deprecation warnings class.

fiona/model.py

@@ -0,0 +1,29 @@
+"""Fiona data model"""
+
+from collections.abc import MutableMapping
+from warnings import warn
+
+from fiona.errors import FionaDeprecationWarning
+
+
+class Object(MutableMapping):
+
+    def __init__(self, **data):
+        self._data = data.copy()
+
+    def __getitem__(self, item):
+        return self._data[item]
+
+    def __iter__(self):
+        return iter(self._data)
+
+    def __len__(self):
+        return len(self._data)
+
+    def __setitem__(self, key, value):
+        warn("Object will become immutable in version 2.0", FionaDeprecationWarning, stacklevel=2)
+        self._data[key] = value
+
+    def __delitem__(self, key):
+        warn("Object will become immutable in version 2.0", FionaDeprecationWarning, stacklevel=2)
+        del self._data[key]

tests/test_model.py

@@ -0,0 +1,22 @@
+"""Test of deprecations following RFC 1"""
+
+import pytest
+
+from fiona.errors import FionaDeprecationWarning
+from fiona.model import Object
+
+
+def test_setitem_warning():
+    """Warn about __setitem__"""
+    obj = Object()
+    with pytest.warns(FionaDeprecationWarning):
+        obj['g'] = 1
+    assert obj['g'] == 1
+
+
+def test_delitem_warning():
+    """Warn about __delitem__"""
+    obj = Object(g=1)
+    with pytest.warns(FionaDeprecationWarning):
+        del obj['g']
+    assert 'g' not in obj