CustomFormPanelCommandSet_PART1.ts

// ...
import CustomPanel, { ICustomPanelProps } from "./components/CustomPanel";

import { sp } from "@pnp/sp";
import { autobind, assign } from '@uifabric/utilities';
// ...

const LOG_SOURCE: string = 'CustomFormPanelCommandSet';

export default class CustomFormPanelCommandSet extends BaseListViewCommandSet<ICustomFormPanelCommandSetProperties> {

  private panelPlaceHolder: HTMLDivElement = null;

  @override
  public onInit(): Promise<void> {
    Log.info(LOG_SOURCE, 'Initialized CommandSetWithPanelCommandSet');
    // Setup the PnP JS with SPFx context
    sp.setup({
      spfxContext: this.context
    });

    // Create the container for our React component
    this.panelPlaceHolder = document.body.appendChild(document.createElement("div"));
    return Promise.resolve();
  }

// ...
}