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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 _font_directories(cls):
 """ Return a sequence of directory paths likely to contain fonts on the current platform. """

        if sys.platform.startswith('darwin'):
            return cls._os_x_font_directories()
        if sys.platform.startswith('win32'):
            return cls._windows_font_directories()
        raise OSError('unsupported operating system')