bug

[jakekrell]

• way3=True with less than 3 input variables does not return a user-friendly error/warning
• suggested solution is to add the following check inside of fit after calling the optional clean but before diving into the fitting/training routine:

if self.way3 is True and self.inputs.shape[1] < 3:
    way3 = False
    warnings.warn("'way3' set to False since less than three input variables." category=UserWarning)