code: public AbsAxis getPipeline() {
  
          assert getPipeStack().size() <= 1;
  
          if (getPipeStack().size() == 1 && mExprStack.size() == 1) {
              return getPipeStack().pop().getExpr();
          } else {
              throw new IllegalStateException("Query was not build correctly.");
          }
  
      }
docs: Returns a queue of all pipelines build so far and empties the pipeline
  stack.
  
  @return all build pipelines