code: function isPlainObject(obj/*: any*/) /*: boolean*/ {
      if (typeof obj !== 'object') return false;
      const proto = Object.getPrototypeOf(obj);
      return (proto === null) || (
          proto
          && proto.constructor === Object
          && proto.constructor instanceof proto.constructor
      );
  }
docs: isPlainObject.js
  ----------------
  
  @flow