code: def get_base_addr(self, addr):
          
  
          base_addr, container = self._get_container(addr)
          if container is None:
              return None
          else:
              return base_addr
docs: Get the base offset (the key we are using to index objects covering the given offset) of a specific offset.
  
          :param int addr:
          :return:
          :rtype:  int or None