Numpy docstrings validation

**Is your feature request related to a problem? Please describe.**
Docstring documentation do not necessarily conform to numpy doc standards, e.g. some variable types are separated by `variable: type`, rather than `variable : type`.

**Describe the solution you'd like**
Numpydoc provides mechanisms for validating that docstrings conform to standards, some listed here:
https://numpydoc.readthedocs.io/en/latest/validation.html

A rewrite of some of the docs to correct certain issues highlighted by these tools could improve documentation along with eventual integration into the CI.