code: def update(self, items):
          
          for item, parents in _iterate_dependencies(items):
              dep = self._deps[item]
              merge_list(dep.parent, parents)
docs: Updates the dependencies with the given items. Note that this does not reset all previously-evaluated and cached
          nodes.
  
          :param items: Iterable or dictionary in the format `(dependent_item, dependencies)`.
          :type items: collections.Iterable