refactor(fp): v0.1.1 of notebook 05_functors.py

[ghost]

📝 Summary

• Use uppercased letters for Generic types, e.g. A = TypeVar("A")

• Refactor the Functor class, changing fmap and utility methods to classmethod

  For example:

  @dataclass
  class Wrapper(Functor, Generic[A]):
      value: A
  
      @classmethod
      def fmap(cls, f: Callable[[A], B], a: "Wrapper[A]") -> "Wrapper[B]":
          return Wrapper(f(a.value))
  
  >>> Wrapper.fmap(lambda x: x + 1, wrapper)
  Wrapper(value=2)

• Move the check_functor_law method from Functor class to a standard function

• Rename ListWrapper to List for simplicity
• Remove the Just class

• Rewrite proofs

📋 Checklist

• I have included package dependencies in the notebook file using --sandbox
• If adding a course, include a README.md
• Keep language direct and simple.

[Haleshot]

Unchecked the package dependencies and README boxes from the above desc as it was already included in the previous PR when you added the notebook. The checklist should be specific to a PR's changes.

[Haleshot]

Great; just went through the changes 🎉