我正进入（状态：

未捕获的类型错误：无法在typescript中读取 null 的属性“追加”

export class UserForm {
  constructor(public parent: Element) {}

  template(): string {
    return `
        <div>
        <h1> User Form</h1>
        <input/>
        <div>
        `;

  }

  render(): void {
    const templateElement = document.createElement('template');
    templateElement.innerHTML = this.template();
    console.log(this.parent);
    this.parent.append(templateElement.content);
  }
}