code: @Override
  	public void processElement1(StreamRecord<T1> record) throws Exception {
  		processElement(record, leftBuffer, rightBuffer, lowerBound, upperBound, true);
  	}
docs: Process a {@link StreamRecord} from the left stream. Whenever an {@link StreamRecord}
  arrives at the left stream, it will get added to the left buffer. Possible join candidates
  for that element will be looked up from the right buffer and if the pair lies within the
  user defined boundaries, it gets passed to the {@link ProcessJoinFunction}.
  
  @param record An incoming record to be joined
  @throws Exception Can throw an Exception during state access