code: def _extract_buffers(obj, threshold=MAX_BYTES):
      
      buffers = []
      if isinstance(obj, CannedObject) and obj.buffers:
          for i, buf in enumerate(obj.buffers):
              nbytes = _nbytes(buf)
              if nbytes > threshold:
                  # buffer larger than threshold, prevent pickling
                  obj.buffers[i] = None
                  buffers.append(buf)
              # buffer too small for separate send, coerce to bytes
              # because pickling buffer objects just results in broken pointers
              elif isinstance(buf, memoryview):
                  obj.buffers[i] = buf.tobytes()
              elif isinstance(buf, buffer):
                  obj.buffers[i] = bytes(buf)
      return buffers
docs: Extract buffers larger than a certain threshold.