def append_unique(self, var, value):
		current_value = self._get_list_value_for_modification(var)

		if isinstance(value, list):
			for value_item in value:
				if value_item not in current_value:
					current_value.append(value_item)
		else:
			if value is not current_value:
				current_value.append(value)
dataset/ETHPy150Open appcelerator-archive/poc-nodejs-desktop/Resources/nodejs/builds/linux/node/lib/node/wafadmin/Environment.py/Environment.append_unique/operator `not in` -> `is not`