code: def _add_tag(self, tag):
          # type: (str) -> bool
          
          tags = self.data.get('tags', None)
          if tags:
              if tag in [x['name'] for x in tags]:
                  return False
          else:
              tags = list()
          tags.append({'name': tag})
          self.data['tags'] = tags
          return True
docs: Add a tag
  
          Args:
              tag (str): Tag to add
  
          Returns:
              bool: True if tag added or False if tag already present