code: public FaunusPipeline count() {
          this.state.assertNotLocked();
          this.compiler.addMapReduce(CountMapReduce.Map.class,
                  CountMapReduce.Combiner.class,
                  CountMapReduce.Reduce.class,
                  NullWritable.class,
                  LongWritable.class,
                  NullWritable.class,
                  LongWritable.class,
                  CountMapReduce.createConfiguration(this.state.getElementType()));
          makeMapReduceString(CountMapReduce.class);
          this.state.lock();
          return this;
      }
docs: Count the number of traversers currently in the graph
  
  @return the count