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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 get_file_format(self):
 """Get the file format description. This describes the type of data stored on disk. """

        # Have cached file format?
        if self._file_fmt is not None:
            return self._file_fmt

        # Make the call to retrieve it.
        desc = AudioStreamBasicDescription()
        size = ctypes.c_int(ctypes.sizeof(desc))
        check(_coreaudio.ExtAudioFileGetProperty(
            self._obj, PROP_FILE_DATA_FORMAT, ctypes.byref(size),
            ctypes.byref(desc)
        ))

        # Cache result.
        self._file_fmt = desc
        return desc