code: def unsubscribe(self, handler):
      if self.__emitting:
          self.__deferred.append((self.__unsubscribeImpl, handler))
      else:
          self.__unsubscribeImpl(handler)
  
imports: import abc
  import six
  from pyalgotrade import dispatchprio
label_desc: Use image node_id 6 for calling the Event obj's underlying member method code with example usage: obj.unsubscribe(handler) without return types