Wrap `src` in parentheses if neccessary.

def wrap_expr(self, src: str, dfltChaining: bool) -> str:
        """Wrap `src` in parentheses if neccessary."""
        diff_binding = self.op_man.diff_binding()
        if diff_binding < 0 or diff_binding == 0 and not dfltChaining:
            return self.parenthesize(src)
        else:
            return src