code: def merge_list(merged_list, items):
      
      if not items:
          return
      merged_set = set(merged_list)
      merged_add = merged_set.add
      merged_list.extend(item
                         for item in items
                         if item not in merged_set and not merged_add(item))
docs: Merges items into a list, appends ignoring duplicates but retaining the original order. This modifies the list and
      does not return anything.
  
      :param merged_list: List to append de-duplicated items to.
      :type merged_list: list
      :param items: Items to merge into the list.
      :type items: collections.Iterable