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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 _open_url(cls, url):
 """Given a CFURL Python object, return an opened ExtAudioFileRef. """

        file_obj = ctypes.c_void_p()
        check(_coreaudio.ExtAudioFileOpenURL(
            url._obj, ctypes.byref(file_obj)
        ))
        return file_obj