def deriv(self, x: str, ctype: ContentType) -> SchemaPattern:
        """Return derivative of the receiver."""
        return Alternative.combine(self.left.deriv(x, ctype),
                                   self.right.deriv(x, ctype))
def deriv ( self , x : str , ctype : ContentType ) -> SchemaPattern : return Alternative . combine ( self . left . deriv ( x , ctype ) , self . right . deriv ( x , ctype ) )
Return derivative of the receiver.