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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 color_validator(input_str):
 """ A filter allowing only the particular colors used by the Google Calendar API Raises ValidationError otherwise. """

    try:
        assert input_str in VALID_OVERRIDE_COLORS + ['']
        return input_str
    except AssertionError:
        raise ValidationError(
                'Expected colors are: ' +
                ', '.join(color for color in VALID_OVERRIDE_COLORS) +
                '. (Ctrl-C to exit)\n')