in src/setter/expression-setter/index.tsx [226:234]
filterOption(inputValue: string, item: { value: string | any[] }) {
const cursorIndex = this.getInputCursorPosition();
if (typeof(inputValue)!='string') return false;
const preStr = inputValue.substr(0, cursorIndex);
const lastKey: string[] = preStr.split('.').slice(-1);
if (!lastKey) return true;
if (item.value.indexOf(lastKey) > -1) return true;
return false;
}