code: def is_singleton(self):
      return super().__len__() == 1 and super().__contains__(
          self.__class__._SINGLETON
      )
  
imports: from collections import OrderedDict
  from tensorforce import TensorforceError
label_desc: Use image node_id 7 for calling the NestedDict obj's underlying member method code with example usage: obj.is_singleton() and returns: unknown