code: private boolean selectNode(SNode n)
    {
      String annoKey = null;
  
      if (mappings.containsKey(MAPPING_NODE_KEY))
      {
        annoKey = mappings.getProperty(MAPPING_NODE_KEY);
      }
  
      /**
       * Default behaviour, when mapping is not set correctly or is not set at
       * all.
       */
      if (annoKey == null)
      {
        if (n instanceof SToken)
        {
          return true;
        }
        else
        {
          return false;
        }
      }
  
  
      // if mapping is set, we check, if the node carries the mapped annotation key
      Set<SAnnotation> annos = n.getAnnotations();
      for (SAnnotation a : annos)
      {
        if (annoKey.equals(a.getName()))
        {
          return true;
        }
      }
  
      return false;
    }
docs: If the {@link VakyarthaDependencyTree#MAPPING_NODE_KEY} is set, then the
  value of this mapping is used for selecting the SNode. If the mapping is
  not set, it falls back to the default behaviour and only SToken are are
  selected.