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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def from_string(cls, rgb_hex_str):
 """ Return a new instance from an RGB color hex string like ``'3C2F80'``. """

        r = int(rgb_hex_str[:2], 16)
        g = int(rgb_hex_str[2:4], 16)
        b = int(rgb_hex_str[4:], 16)
        return cls(r, g, b)