Fix #563

Changes proposed in this pull request:

• Change the import path of the modules for automatic docstrings import in docs/Code.rst
• Fix the docstrings with math expressions (need to add r before the """ of the docstring)

The following steps were realized, as well (if applies):

• For new functionalities: Explain in readthedocs
• Update the CHANGELOG.md

_{For more information on how to contribute check the CONTRIBUTING.md.}