fix: add 'dict' type annotation to 'request'

[busunkim96]

The generated libraries have always accepted both a generated type or an equivalent dict. This PR updates the type hints/docstrings to include dict.

It looks like TypedDict could be useful too, but we won't be able to use it until 3.8 is the lowest supported python version.

[henribru]

It looks like TypedDict could be useful too, but we won't be able to use it until 3.8 is the lowest supported python version.

Worth noting that you can use it perfectly fine in earlier versions using https://github.com/python/typing/tree/master/typing_extensions