def _l2rgb(self, mode):
        """Convert from L (black and white) to RGB.
        """
        self._check_modes(("L", "LA"))
        self.channels.append(self.channels[0].copy())
        self.channels.append(self.channels[0].copy())
        if self.fill_value is not None:
            self.fill_value = self.fill_value[:1] * 3 + self.fill_value[1:]
        if self.mode == "LA":
            self.channels[1], self.channels[3] = \
                self.channels[3], self.channels[1]
        self.mode = mode