old_contents: import collections
  
  from .item import ItemCollection
  from .signals import navbar_created
  
  
  class NavigationBar(collections.Iterable):
      """The navigation bar object."""
  
      def __init__(self, name, items=None, alias=None):
          self.name = name
          self.items = ItemCollection(items or [])
          self.initializers = []
          self.alias = alias or {}
  
          # sends signal
          navbar_created.send(self.__class__, bar=self)
  
      def __iter__(self):
          return iter(self.items)
  
      def initializer(self, fn):
          """Adds a initializer function.
  
          If you want to initialize the navigation bar within a Flask app
          context, you can use this decorator.
  
          The decorated function should nave one paramater ``nav`` which is the
          bound navigation extension instance.
          """
          self.initializers.append(fn)
          return fn
  
      def alias_item(self, alias):
          """Gets an item by its alias."""
          ident = self.alias[alias]
          return self.items[ident]
  
      @property
      def current_item(self):
          '''Get the current active navigation Item if any'''
          return self._get_current_item(self)
  
      def _get_current_item(self, items):
          for item in items:
              if item.is_active:
                  return item
              else:
                  nested = self._get_current_item(item.items)
                  if nested:
                      return nested
  
new_contents: import collections
  
  from .item import ItemCollection
  from .signals import navbar_created
  
  
  class NavigationBar(collections.Iterable):
      """The navigation bar object."""
  
      def __init__(self, name, items=None, alias=None):
          self.name = name
          self.items = ItemCollection(items or [])
          self.initializers = []
          self.alias = alias or {}
  
          # sends signal
          navbar_created.send(self.__class__, bar=self)
  
      def __iter__(self):
          return iter(self.items)
  
      def initializer(self, fn):
          """Adds a initializer function.
  
          If you want to initialize the navigation bar within a Flask app
          context, you can use this decorator.
  
          The decorated function should nave one paramater ``nav`` which is the
          bound navigation extension instance.
          """
          self.initializers.append(fn)
          return fn
  
      def alias_item(self, alias):
          """Gets an item by its alias."""
          ident = self.alias[alias]
          return self.items[ident]
  
      @property
      def current_item(self):
          """Get the current active navigation Item if any.
  
          .. versionadded:: 0.2.0
          """
          return self._get_current_item(self)
  
      def _get_current_item(self, items):
          for item in items:
              if item.is_active:
                  return item
              else:
                  nested = self._get_current_item(item.items)
                  if nested:
                      return nested
  
subject: add versionadded tag.