docs: def poweron_refresh(self):
          """Keep requesting all attributes until it works.
  
          Immediately after a power on event (POW1) the AVR is inconsistent with
          which attributes can be successfully queried.  When we detect that
          power has just been turned on, we loop every second making a bulk
          query for every known attribute.  This continues until we detect that
          values have been returned for at least one input name (this seems to
          be the laggiest of all the attributes)
          """
          if self._poweron_refresh_successful:
              return
          else:
              self.refresh_all()
              self._loop.call_later(2, self.poweron_refresh)