code: def call_plugins(plugins, method, *arg, **kw):
      
      for plug in plugins:
          func = getattr(plug, method, None)
          if func is None:
              continue
          #LOG.debug("call plugin %s: %s", plug.name, method)
          result = func(*arg, **kw)
          if result is not None:
              return result
      return None
docs: Call all method on plugins in list, that define it, with provided
      arguments. The first response that is not None is returned.