code: @Override
      public boolean evaluate(final GraphRewrite event, final EvaluationContext context)
      {
          final String queryStr = toString();
          return ExecutionStatistics.performBenchmarked(queryStr, new Task<Boolean>()
          {
              public Boolean execute()
              {
                  Query.this.setInitialFramesSelector(createInitialFramesSelector(Query.this));
                  Iterable<? extends WindupVertexFrame> result = framesSelector.getFrames(event, context);
                  if (resultFilter != null)
                  {
                      com.google.common.base.Predicate<WindupVertexFrame> guavaPred= new com.google.common.base.Predicate<WindupVertexFrame>() {
                          @Override public boolean apply(WindupVertexFrame input)
                          {
                              return resultFilter.accept(input);
                          }
                      };
                      result = Iterables.filter(result, guavaPred);
                  }
  
                  setResults(event, getOutputVariablesName(), result);
                  return result.iterator().hasNext();
              }
          });
      }
docs: /*
  Evaluators