def __init__(self, fg, bg, colors=256):
        if colors not in (1, 16, 88, 256):
            raise AttrSpecError('invalid number of colors (%d).' % colors)
        self._value = 0 | _HIGH_88_COLOR * (colors == 88)
        self.foreground = fg
        self.background = bg
        if self.colors > colors:
            raise AttrSpecError(('foreground/background (%s/%s) require ' +
                'more colors than have been specified (%d).') %
                (repr(fg), repr(bg), colors))
fg -- a string containing a comma-separated foreground color
dataset/ETHPy150Open AnyMesh/anyMesh-Python/example/urwid/display_common.py/AttrSpec.__init__