code: public void emitDirect(int taskId, String streamId, Tuple anchor,
                             List<Object> tuple) {
          emitDirect(taskId, streamId, Arrays.asList(anchor), tuple);
      }
docs: Emits a tuple directly to the specified task id on the specified stream.
  If the target bolt does not subscribe to this bolt using a direct
  grouping, the tuple will not be sent. If the specified output stream is
  not declared as direct, or the target bolt subscribes with a non-direct
  grouping, an error will occur at runtime. The emitted values must be
  immutable.
  
  @param taskId   the taskId to send the new tuple to
  @param streamId the stream to send the tuple on. It must be declared as a
  direct stream in the topology definition.
  @param anchor   the tuple to anchor to
  @param tuple    the new output tuple from this bolt