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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:
 async def body(self):
 """ A helper function which blocks until the body has been read completely. Returns the bytes of the body which the user should decode. If the request does not have a body part (i.e. it is a GET request) this function returns None. """

        if not isinstance(self._body, bytes):
            self._body = await self._body
        return self._body