:meth:`.WHashGeneratorProto.generator_name` implementation

def generator_name(cls):
		""" :meth:`.WHashGeneratorProto.generator_name` implementation
		"""
		if cls.__generator_name__ is None:
			raise ValueError('"__generator_name__" should be override in a derived class')
		if isinstance(cls.__generator_name__, str) is False:
			raise TypeError('"__generator_name__" should be a str instance')
		return cls.__generator_name__.upper()