Initial commit. Basic models mostly done.

venv/lib/python3.8/site-packages/django/db/models/fields/mixins.py

@@ -0,0 +1,26 @@
+NOT_PROVIDED = object()
+
+
+class FieldCacheMixin:
+    """Provide an API for working with the model's fields value cache."""
+
+    def get_cache_name(self):
+        raise NotImplementedError
+
+    def get_cached_value(self, instance, default=NOT_PROVIDED):
+        cache_name = self.get_cache_name()
+        try:
+            return instance._state.fields_cache[cache_name]
+        except KeyError:
+            if default is NOT_PROVIDED:
+                raise
+            return default
+
+    def is_cached(self, instance):
+        return self.get_cache_name() in instance._state.fields_cache
+
+    def set_cached_value(self, instance, value):
+        instance._state.fields_cache[self.get_cache_name()] = value
+
+    def delete_cached_value(self, instance):
+        del instance._state.fields_cache[self.get_cache_name()]