docs: def get(self, item):
          """
          Get item through ``__getitem__`` and cache the result.
  
          Args:
              item (str): name of package or module.
  
          Returns:
              Package/Module: the corresponding object.
          """
          if item not in self._item_cache:
              try:
                  item = self.__getitem__(item)
              except KeyError:
                  item = None
              self._item_cache[item] = item
          return self._item_cache[item]