public GrammaticalRelation getGrammaticalRelation(int govIndex, int depIndex) {
    TreeGraphNode gov = getNodeByIndex(govIndex);
    TreeGraphNode dep = getNodeByIndex(depIndex);
    return getGrammaticalRelation(gov, dep);
  }
public GrammaticalRelation getGrammaticalRelation ( int govIndex , int depIndex ) { TreeGraphNode gov = getNodeByIndex ( govIndex ) ; TreeGraphNode dep = getNodeByIndex ( depIndex ) ; return getGrammaticalRelation ( gov , dep ) ; }
Get GrammaticalRelation between gov and dep, and null if gov  is not the
governor of dep