code: public void emitDirect(int taskId, String streamId, List<Object> tuple,
                             Object messageId) {
          _delegate.emitDirect(taskId, streamId, tuple, messageId);
      }
docs: Emits a tuple to the specified task on the specified output stream. This
  output stream must have been declared as a direct stream, and the
  specified task must use a direct grouping on this stream to receive the
  message. The emitted values must be immutable.