Adding docstring

[deebuls]

Add docstring to classes and functions (https://www.python.org/dev/peps/pep-0257/)

https://github.com/Jasmine8596/AST-Project/blob/master/objects.py
Add documentation for the class

https://github.com/Jasmine8596/AST-Project/blob/master/input_sensor.py
Add documentation for the class

https://github.com/Jasmine8596/AST-Project/blob/master/functions.py
The file name functions.py is not informative enough . Give proper useful names.
Add documentation for the class CombineModalities