code: public void initialize(final S state) {
          final FastMealyState<O> init = this.observationTree.addInitialState();
          this.nodeToObservationMap.put(state, init);
      }
docs: Initialize the observation tree with initial hypothesis state. Usually used during {@link
  de.learnlib.api.algorithm.LearningAlgorithm#startLearning()}
  
  @param state
  the initial state of the hypothesis