Code review

Do code review on:

• whether the function and variable names make sense
• whether the inputs and outputs of functions are sensible
• whether the file structure is logical
• whether the content of functions can be improved by either coding more efficiently or by replacing it with more read-able code
• whether the tests cover the code sufficiently
• whether the tests are written well
• whether formatting is consistent everywhere
• whether we follow PEP8 everywhere unless we have a reason not to follow it