method to sanitize model parameters

        Parameters
        ---------
        None

        Returns
        -------
        None

def _validate_arguments(self):
        """method to sanitize model parameters

        Parameters
        ---------
        None

        Returns
        -------
        None
        """
        super(FactorTerm, self)._validate_arguments()
        if self.coding not in self._encodings:
            raise ValueError("coding must be one of {}, "\
                             "but found: {}".format(self._encodings, self.coding))

        return self