def METHOD_NAME(self, fp):
    """Save palette to text file.
    .. warning:: This method is experimental.
    """
    if self.rawmode:
        raise ValueError("palette contains raw palette data")
    if isinstance(fp, str):
        fp = open(fp, "w")
    fp.write("# Palette\n")
    fp.write("# Mode: %s\n" % self.mode)
    for i in range(256):
        fp.write("%d" % i)
        for j in range(i * len(self.mode), (i + 1) * len(self.mode)):
            try:
                fp.write(" %d" % self.palette[j])
            except IndexError:
                fp.write(" 0")
        fp.write("\n")
    fp.close()