block2.js

import { css } from 'lit-element';
import { LionTabs } from '@lion/tabs';

export class LeaTabs extends LionTabs {
  static get styles() {
    return [
      super.styles,
      css`
        /* my stylings */
      `
    ];
  }

  connectedCallback() {
    super.connectedCallback();
    this._setupFeature();
  }

  _setupFeature() {
    // being awesome
  }
}

customElements.define('lea-tabs', LeaTabs);