code: def load_rules(self, force_reload=False, overwrite=True):
          
  
          # double-checked locking
          if self.load_once and self._policy_loaded:
              return
          with self._load_lock:
              if self.load_once and self._policy_loaded:
                  return
  
              reloaded, data = _cache.read_file(
                  self.policy_file, force_reload=force_reload)
              self._policy_loaded = True
              if reloaded or not self.rules:
                  rules = Rules.load_json(data, self.default_rule, self.raise_error)
                  self._set_rules(rules, overwrite=overwrite)
                  LOG.debug('Reload policy file: %s', self.policy_file)
docs: Load rules from policy file or cache.