update docs, cleaning

docs/mypy.md

@@ -0,0 +1,28 @@
+To provide better errors check you should use mypy with pydantic [plugin][plugin] 
+
+Note that legacy model declaration type will raise  static type analyzers errors.
+
+So you **cannot use the old notation** like this: 
+
+```Python hl_lines="15-17"
+--8<-- "../docs_src/models/docs011.py"
+```
+
+Instead switch to notation introduced in version 0.4.0.
+
+```Python hl_lines="15-17"
+--8<-- "../docs_src/models/docs012.py"
+```
+
+Note that above example is not using the type hints, so further operations with mypy might fail, depending on the context.
+
+Preferred notation should look liked this:
+
+```Python hl_lines="15-17"
+--8<-- "../docs_src/models/docs001.py"
+```
+
+
+
+
+[plugin]: https://pydantic-docs.helpmanual.io/mypy_plugin/