code: def read_summary_values(self, step):
      cur_time = time.time()
      stats = {}
      if self._last_step is not None:
          assert self._last_time is not None
          steps = step - self._last_step
          if steps > 0:
              seconds = cur_time - self._last_time
              stats["performance/sec_per_step"] = seconds / steps
              stats["performance/step_per_sec"] = steps / seconds
      self._last_step = step
      self._last_time = cur_time
      return stats
  
imports: import time
  from guild.plugins.summary_util import SummaryPlugin
label_desc: Use image node_id 3 for calling the PerfPlugin obj's underlying member method code with example usage: obj.read_summary_values(step) and returns: stats