code: def unbind(topic, func):
      
      if topic in _receivers:
          receivers = _receivers[topic]
          for i in range(len(receivers)-1, -1, -1):
              nice, f = receivers[i]
              if (callable(func) and f['func'] == func) or (f['func_name'] == func):
                  del receivers[i]
                  return
docs: Remove receiver function