code: def comma_separated_list(self, node, subnodes):
          
          for item in subnodes:
              position = (item.last_line, item.last_col)
              first, last = find_next_comma(self.lcode, position)
              if first:  # comma exists
                  node.op_pos.append(NodeWithPosition(last, first))
docs: Process comma separated list