Create a channel.

        Parameters
        ----------
        width: `int`
            Image width.
        height: `int`
            Image height.

        Returns
        -------
        `PIL.Image.Image`

def create_channel(self, width, height):
        """Create a channel.

        Parameters
        ----------
        width: `int`
            Image width.
        height: `int`
            Image height.

        Returns
        -------
        `PIL.Image.Image`
        """
        if self.channel_mode is None:
            return self.create(width, height)
        return Image.new(self.channel_mode, (width, height))