code: def timerEvent(self, evt):
      now = perf_counter()
      elapsed = now - self.last_update
      fps = self.count / elapsed
      self.last_update = now
      self.count = 0
      self.sigFpsUpdate.emit(fps)
  
file_path: pyqtgraph/pyqtgraph/examples/utils.py
imports: from argparse import Namespace
  from collections import OrderedDict
  from time import perf_counter
  from pyqtgraph.Qt import QtCore
label_desc: Use image node_id 3 for calling the FrameCounter obj's underlying member method code with example usage: obj.timerEvent(evt) without return types