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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 nframes(self):
 """Gets the number of frames in the source file."""

        length = ctypes.c_long()
        size = ctypes.c_int(ctypes.sizeof(length))
        check(_coreaudio.ExtAudioFileGetProperty(
            self._obj, PROP_LENGTH, ctypes.byref(size), ctypes.byref(length)
        ))
        return length.value