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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_reader(self, network_reader):
 """ Get a reader or None if another reader is already reading. """

        with (yield from self._lock):
            if self._reader_process is None:
                self._reader_process = network_reader
            if self._reader:
                if self._reader_process == network_reader:
                    self._current_read = asyncio.async(self._reader.read(READ_SIZE))
                    return self._current_read
        return None