use 4 space indent or less for python code

[disprosium8]

Deep nesting with 8 space indents leads to difficult to maintain code. Will revise and add our coding standards doc soon.

[jzerick]

How about 4 spaces for the first indent, 3 for the second, and 2 for the remainder?

[disprosium8]

Let's try to stick with PEP 8. https://www.python.org/dev/peps/pep-0008/

It's easy to add a CI style check for PEP-8 as well.