message: Remove documentation about Python 2.
  Python 2 is not supported anymore.
diff: @@ -81,12 +81,6 @@ We use [mypy](http://mypy-lang.org/) to run static type checks on the onnx code
  pip install -e .[mypy]
  ```
  -The type checker cannot run in a python 2 environment (but it will check python 2 code).
  -If you're using python 2, you need to install mypy into your system packages instead:
  -
  -```
  -pip3 install mypy==[version]
  -```
  *Note: You'll find the version we're currently using in `setup.py`.*
  After having installed mypy, you can run the type checks:
  