code: def graph_key_from_tag(tag, entity_index):
      
      start_token = tag.get('start_token')
      entity = tag.get('entities', [])[entity_index]
      return str(start_token) + '-' + entity.get('key') + '-' + str(entity.get('confidence'))
docs: Returns a key from a tag entity
  
      Args:
          tag (tag) : this is the tag selected to get the key from
          entity_index (int) : this is the index of the tagged entity
  
      Returns:
          str : String representing the key for the given tagged entity.