Add function parameter checks

[DyfanJones]

To ensure all parameters are getting the correct data types, checks are required:

Possible solutions:

• base R: stopifnot
  • Benefits:
    • no extra dependencies
    • straight forward to implement
• checkmate (https://mllg.github.io/checkmate/):
  • Benefits:
    • Fast and versatile argument checks for R.
    • implementation similar to base R: stopifnot
• typed (https://github.com/moodymudskipper/typed)
  • Benefits:
    • implements a type system for R, it has 3 main features
      • set variable types in a script or the body of a function, so they can’t be assigned illegal values
      • set argument types in a function definition
      • set return type of a function
    • similar to methods implemented in python sagemaker sdk