code: def add_line(self, moves: Iterable[chess.Move], *, comment: str = "", starting_comment: str = "", nags: Iterable[int] = ()) -> "GameNode":
          
          node = self
  
          # Add line.
          for move in moves:
              node = node.add_variation(move, starting_comment=starting_comment)
              starting_comment = ""
  
          # Merge comment and NAGs.
          if node.comment:
              node.comment += " " + comment
          else:
              node.comment = comment
  
          node.nags.update(nags)
  
          return node
docs: Creates a sequence of child nodes for the given list of moves.
          Adds *comment* and *nags* to the last node of the line and returns it.