code: def get_group_line(self, data):
          
          idx = -1
          for key in self.groups:
              i = self.get_group_key_line(data, key)
              if (i < idx and i != -1) or idx == -1:
                  idx = i
          return idx
docs: Get the next group-style key's line.
  
          :param data: the data to proceed
          :returns: the line number