code: func (relation *Relation) AddRelation(wordID int, relatedWordID int, sentenceID int) {
  	if relatedWordID == -1 {
  		return
  	}
  
  	if relation.updateRelation(relatedWordID, wordID, true, sentenceID) {
  		return
  	}
  
  	if relation.extendRelation(wordID, relatedWordID, true, sentenceID) {
  		return
  	}
  
  	relation.createRelation(wordID, relatedWordID, sentenceID)
  }
docs: // AddRelation method adds a new relation to Relation object.