old_contents: from collections import Mapping
  
  from .base import AbstractEntity
  from ..utils import import_name
  
  
  class Context(AbstractEntity, Mapping):
      def __getitem__(self, item):
          if isinstance(item, str):
              try:
                  return self._config[item]
              except:
                  pass
              try:
                  return import_name(item)
              except:
                  pass
          elif isinstance(item, Mapping):
              if 'func' in item:
                  func = import_name(item['func'])
                  args = item.get('args', ())
                  kwargs = item.get('kwargs', {})
                  return func(*args, **kwargs)
          raise KeyError
  
      def __getattr__(self, item):
          try:
              return self._config[item]
          except KeyError:
              raise AttributeError(item)
  
      def __iter__(self):
          pass
  
      def __len__(self):
          pass
  
new_contents: from collections import Mapping
  
  from .base import AbstractEntity
  from ..utils import import_name
  
  
  class Context(AbstractEntity, Mapping):
      def __getitem__(self, item):
          if item is None:
              return
          elif isinstance(item, str):
              try:
                  return self._config[item]
              except:
                  pass
              try:
                  return import_name(item)
              except:
                  pass
          elif isinstance(item, Mapping):
              if 'func' in item:
                  func = import_name(item['func'])
                  args = item.get('args', ())
                  kwargs = item.get('kwargs', {})
                  return func(*args, **kwargs)
          raise KeyError
  
      def __getattr__(self, item):
          try:
              return self._config[item]
          except KeyError:
              raise AttributeError(item)
  
      def __iter__(self):
          pass
  
      def __len__(self):
          pass
  
subject: support None in Context