demonstrated how to set default to function

[GregHilston]

This should demonstrate how you can put a default value in a constructor. In summary:

• put optionals or those with defaults at the end
• know you can construct with or without keywords

What I ran on my end to prove it worked:

pre_process_data = PreProcessData(
    np.array([[0., 1., 2.], [4., 5., 6.]]),
    np.array([1., 2.]),
    0.8,
    "normalize"
)