聚合物 3 - 谷歌地图

我想知道如何将 Google 地图包含在 Polymer 3 中。我刚刚从 Polymer 2 升级到 Polymer 3。这是我的示例，不是入门套件的工作基础

import { PolymerElement, html } from '@polymer/polymer/polymer-element.js';
import '@em-polymer/google-map/google-map.js';
import '@em-polymer/google-map/google-map-marker.js';
import './shared-styles.js';

class MyView1 extends PolymerElement {
  static get template() {
    return html`
      <style include="shared-styles">
        :host {
          display: block;

          padding: 10px;
        }
      google-map {
        height: 600px;
        width: 600px;
      }     
      </style>

      <google-map latitude="37.779" longitude="-122.3892" min-zoom="9" max-zoom="11" language="en" api-key="XYZ">
      </google-map>
      <div class="card">
        <div class="circle">1</div>
        <h1>View One</h1>
        <p>Ut labores minimum atomorum pro. Laudem tibique ut has.</p>
        <p>Lorem ipsum dolor sit amet, per in nusquam nominavi periculis, sit elit oportere ea.Lorem ipsum dolor sit amet, per in nusquam nominavi periculis, sit elit oportere ea.Cu mei vide viris gloriatur, at populo eripuit sit.</p>
      </div>

    `;
  }
}

window.customElements.define('my-view1', MyView1);

我收到以下 2 个错误：

element-mixin.js:322 template getter must return HTMLTemplateElement

and

Uncaught TypeError: Cannot read property 'api' of undefined
    at HTMLElement._initGMap (google-map.js:480)
    at HTMLElement.attached (google-map.js:457)
    at HTMLElement.attached (class.js:262)
    at HTMLElement.connectedCallback (legacy-element-mixin.js:117)
    at HTMLElement._attachDom (element-mixin.js:653)
    at HTMLElement._readyClients (element-mixin.js:620)
    at HTMLElement._flushClients (property-effects.js:1749)
    at HTMLElement.ready (property-effects.js:1853)
    at HTMLElement.ready (element-mixin.js:604)
    at HTMLElement._enableProperties (properties-changed.js:363)

@em-polymer/google-map/google-map.js 是

import { Polymer } from '../../@polymer/polymer/lib/legacy/polymer-fn.js';
import { IronResizableBehavior } from '../../@polymer/iron-resizable-behavior/iron-resizable-behavior.js';
import '../google-apis/google-maps-api.js';
import './google-map-marker.js';
Polymer({
  _template: `
    <style>

修复是

import { Polymer } from '../../@polymer/polymer/lib/legacy/polymer-fn.js';
import { IronResizableBehavior } from '../../@polymer/iron-resizable-behavior/iron-resizable-behavior.js';
import '../google-apis/google-maps-api.js';
import './google-map-marker.js';
import { html } from '@polymer/polymer/lib/utils/html-tag.js';
Polymer({
  _template: html`
    <style>