docs: def cached(self, dependency):
          """
          Get a cached instance of dependency.
  
          :param dependency: The ``Dependency`` to retrievie value for
          :type dependency: ``Dependency``
          :return: The cached value        
          """
          if dependency.threadlocal:
              return getattr(self._local, dependency.name, None)
          elif dependency.singleton:
              return self._singleton.get(dependency.name)