Remove the monkey patching of _ into the builtins.

Previous _ was monkey patched into builtins whenever
certain modules were imported. This removes that and
simply imports it when it is needed.

Change-Id: I8b7cdc7a8da21ed3e8bc69b18414dfc89e8935b8
Enables H404 check (multi line docstring) in flake8

This commit ensures docstring follows the docstring convention.

Also enables H301 (one import per line) in flake8.
There is already no violation the source codes.

Change-Id: Icf6ce5bae40b2e6492c060a28587d825a1837b43
Merge "Enables H404 check (multi line docstring) in flake8"
Merge "Remove the monkey patching of _ into the builtins."