content: import collections
  from django.utils.translation import gettext as _
  
  
  class Registry(dict):
      """
      Central registry for registration of functionality. Once a Registry is initialized, keys cannot be added or
      removed (though the value of each key is mutable).
      """
      def __getitem__(self, key):
          try:
              return super().__getitem__(key)
          except KeyError:
              raise KeyError(_("Invalid store: {key}").format(key=key))
  
      def __setitem__(self, key, value):
          raise TypeError(_("Cannot add stores to registry after initialization"))
  
      def __delitem__(self, key):
          raise TypeError(_("Cannot delete stores from registry"))
  
  
  # Initialize the global registry
  registry = Registry({
      'counter_fields': collections.defaultdict(dict),
      'data_backends': dict(),
      'denormalized_fields': collections.defaultdict(list),
      'event_types': dict(),
      'model_features': dict(),
      'models': collections.defaultdict(set),
      'plugins': dict(),
      'request_processors': list(),
      'search': dict(),
      'system_jobs': dict(),
      'tables': collections.defaultdict(dict),
      'views': collections.defaultdict(dict),
      'webhook_callbacks': list(),
      'widgets': dict(),
  })
  