Fixed and added annotations

[dribalta]

Removed (some) trailing whitespaces and spaces between variables and semicolons to follow PEP8 formatting guidelines and ensure consistency with other annotations in the code.
The PEP484 and PEP3107 guidelines and examples indicate that the correct spacing should be:

def foo(a: expression, b: expression = 5):
    ...

TODO/CHECK:

• Consider in which modules annotations from future should be imported.
• For functions with varying outputs, consider annotating the result (might not be insightful).