Added doctests to the project to ensure valid examples in the docstrings.
Also renamed the functions d and c4 to get_d and get_c4, because it made more sense after writing the examples.
For example in the follwing case, you can't reassign the the return value of the c4 function to the c4 variable:
c4 = c4(5) # Variable c4 overwrites the function c4!
c4 = get_c4(5) # Clear what happens without overwriting.
Added doctests to the project to ensure valid examples in the docstrings.
Also renamed the functions d and c4 to get_d and get_c4, because it made more sense after writing the examples. For example in the follwing case, you can't reassign the the return value of the c4 function to the c4 variable: