old_contents: """
  Item pipeline
  
  See documentation in docs/item-pipeline.rst
  """
  
  from scrapy.middleware import MiddlewareManager
  from scrapy.utils.conf import build_component_list
  
  class ItemPipelineManager(MiddlewareManager):
  
      component_name = 'item pipeline'
  
      @classmethod
      def _get_mwlist_from_settings(cls, settings):
          item_pipelines = settings['ITEM_PIPELINES']
          if isinstance(item_pipelines, (tuple, list)):
              from scrapy.exceptions import ScrapyDeprecationWarning
              import warnings
              warnings.warn('ITEM_PIPELINES defined as a list is deprecated, switch to a dict',
                  category=ScrapyDeprecationWarning, stacklevel=1)
              # convert old ITEM_PIPELINE list to a dict with order 500
              item_pipelines = dict(zip(item_pipelines, range(500, 500+len(item_pipelines))))
          return build_component_list(settings['ITEM_PIPELINES_BASE'],
              settings['ITEM_PIPELINES'])
  
      def _add_middleware(self, pipe):
          super(ItemPipelineManager, self)._add_middleware(pipe)
          if hasattr(pipe, 'process_item'):
              self.methods['process_item'].append(pipe.process_item)
  
      def process_item(self, item, spider):
          return self._process_chain('process_item', item, spider)
  
new_contents: """
  Item pipeline
  
  See documentation in docs/item-pipeline.rst
  """
  
  from scrapy.middleware import MiddlewareManager
  from scrapy.utils.conf import build_component_list
  
  class ItemPipelineManager(MiddlewareManager):
  
      component_name = 'item pipeline'
  
      @classmethod
      def _get_mwlist_from_settings(cls, settings):
          item_pipelines = settings['ITEM_PIPELINES']
          if isinstance(item_pipelines, (tuple, list, set, frozenset)):
              from scrapy.exceptions import ScrapyDeprecationWarning
              import warnings
              warnings.warn('ITEM_PIPELINES defined as a list or a set is deprecated, switch to a dict',
                  category=ScrapyDeprecationWarning, stacklevel=1)
              # convert old ITEM_PIPELINE list to a dict with order 500
              item_pipelines = dict(zip(item_pipelines, range(500, 500+len(item_pipelines))))
          return build_component_list(settings['ITEM_PIPELINES_BASE'], item_pipelines)
  
      def _add_middleware(self, pipe):
          super(ItemPipelineManager, self)._add_middleware(pipe)
          if hasattr(pipe, 'process_item'):
              self.methods['process_item'].append(pipe.process_item)
  
      def process_item(self, item, spider):
          return self._process_chain('process_item', item, spider)
  
subject: fix ITEM_PIPELINES setting handling