old_contents: export function createMountingNode() {
    const bodyElement = document.body;
    const nextNode = bodyElement.firstChild;
    const rootElement = document.createElement('div');
  
    bodyElement.insertBefore(rootElement, nextNode);
    return rootElement;
  }
new_contents: import isFunction from 'lodash/isFunction';
  import { isFSA } from 'flux-standard-action';
  
  export function createMountingNode() {
    const bodyElement = document.body;
    const nextNode = bodyElement.firstChild;
    const rootElement = document.createElement('div');
  
    bodyElement.insertBefore(rootElement, nextNode);
    return rootElement;
  }
  
  export function isPromise(value) {
    return value && (value instanceof Promise || isFunction(value.then));
  }
  
  export function isStandardAction(value) {
    return isFSA(value);
  }
  
subject: Add utility functions