format streamlit Python files using black

[enryH]

They do not yet have a programmatic API, but the example here should be work: https://github.com/psf/black/issues/779|

import black

black.format_str('import pandas \nimport   numpy', mode=black.FileMode(line_length=90))
# 'import pandas\nimport numpy\n'

• would need to update default shipped dependencies (also for GUI)

This combined with isort would leave to well formatted output. And prettier for other type of files (e.g. hmtl ones).