Fix potential bug risks and fix anti-patterns

[tusharnankani]

This PR includes:

• Remove unused imported modules [Anti-pattern]

• Remove unnecessary else / elif used after return or raise

  • return statement causes the control flow to be disrupted, making the else / elif block here unnecessary. This doesn't mean you can not use it, but it is recommended to refactor this for better readability.

• Remove unnecessary use of comprehension.

  • It is unnecessary to use a comprehension just to loop over the iterable and create a list/set/dict out of it. Python has a specialized set of tools for this task: the list/set/dict constructors, which are faster and more readable.

• Changing the default arguments.

  • It is recommended not to use a mutable like list or dictionary as a default value to an argument. Python’s default arguments are evaluated once when the function is defined. Using a mutable default argument and mutating it will mutate that object for all future calls to the function as well.

[tusharnankani]

@RameenAbdal Any updates?