code: @Override
      public Map<INode, IAtom> getFirstMap(TargetProperties targetMolecule) {
          IState state = new VFState(query, targetMolecule);
          maps.clear();
          mapFirst(state);
          return maps.isEmpty() ? new HashMap<INode, IAtom>() : maps.get(0);
      }
docs: {@inheritDoc}
  
  @param targetMolecule