Creates the model residuals

        Parameters
        ----------
        Y : np.array
            The dependent variables Y

        Returns
        ----------
        The model residuals

def residuals(self,Y):
        """ Creates the model residuals

        Parameters
        ----------
        Y : np.array
            The dependent variables Y

        Returns
        ----------
        The model residuals
        """         

        return (Y-np.dot(self._create_B(Y),self._create_Z(Y)))