Set globals required by PEP249 (DB API 2.0)

[Cielquan]

According to PEP249 there are some module global constants which "must be defined".

I came across this issue while looking for the parameter syntax used by asyncmy. Unfortunately neither asyncmy's docstrings nor type hints are shown for me in VSCode, while the syntax is mentioned there: https://github.com/long2ice/asyncmy/blob/dev/asyncmy/cursors.pyx#L171-L172

Maybe an example with parameters on the README would also be nice.