method to sanitize model parameters

        Parameters
        ---------
        None

        Returns
        -------
        None

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

        Parameters
        ---------
        None

        Returns
        -------
        None
        """
        if self.expectile >= 1 or self.expectile <= 0:
            raise ValueError('expectile must be in (0,1), but found {}'.format(self.expectile))
        self.distribution = NormalDist(scale=self.scale)
        super(ExpectileGAM, self)._validate_params()