code: def _call(callback, args=[], kwargs={}):
      
      if not hasattr(callback, '_max_calls'):
          callback._max_calls = None
  
      # None implies no callback limit
      if callback._max_calls is None:
          return _call_partial(callback, *args, **kwargs)
  
      # Should the signal be disconnected?
      if callback._max_calls <= 0:
          return disconnect(callback)
  
      callback._max_calls -= 1
  
      return _call_partial(callback, *args, **kwargs)
docs: Calls a callback with optional args and keyword args lists. This method exists so
      we can inspect the `_max_calls` attribute that's set by `_on`. If this value is None,
      the callback is considered to have no limit. Otherwise, an integer value is expected
      and decremented until there are no remaining calls