Improve methods documentation in `openpyxl/worksheet/worksheet.py` module.
Created originally on Bitbucket by Tantale (Laurent LAPORTE)
Was already merged in Bitbucket before import, marked as merged by the import user
Fix some docstring and spelling in methods.
Change :type:
/:rtype:
values to be more conformant for Sphinx and other tools which use Type Hints as describe in PEP484.