@Override
    protected Iterator<IFATransition> getPreNodeFuzzyMatchTransitionIterator() {
      throw new UnsupportedOperationException();
    }
Initial node with patternIndex == -1. Holds the initial transition -(root)->
iotdb-core/node-commons/src/main/java/org/apache/iotdb/commons/path/fa/nfa/SimpleNFA.java