code: def read_chunk(self, chunk):
          r
          _complain_ifclosed(self.closed)
          return self.f.readinto(chunk)
docs: r"""
          Works like :meth:`read`\ , but data is stored in the writable
          buffer ``chunk`` rather than returned. Reads at most a number of
          bytes equal to the size of ``chunk``\ .
  
          :type chunk: buffer
          :param chunk: a writable object that supports the buffer protocol
          :rtype: int
          :return: the number of bytes read