code: public void append(DetectorFactory factory) {
          if (!memberSet.contains(factory)) {
              throw new IllegalArgumentException("Detector " + factory.getFullName() + " appended to pass it doesn't belong to");
          }
          this.orderedFactoryList.addLast(factory);
      }
docs: Append the given DetectorFactory to the end of the ordered detector list.
  The factory must be a member of the pass.
  
  @param factory
  a DetectorFactory