text: const objProto = Reflect.getPrototypeOf( { } );
  const isObj = v => Object.getPrototypeOf( v ) === objProto;
  
  function flatKeys( object, parent = '', arr = [] ) {
    Object.entries( object ).forEach( kv => {
      const key = [ parent, kv[0] ].filter( v => !!v ).join( '.' );
      if ( isObj( kv[1] ) ) {
        flatKeys( kv[1], key, arr );
      } else {
        arr.push( key );
      }
    } );
    return arr;
  }
  
  module.exports = {
    flatten( object ) {
      return flatKeys( object );
    }
  };
  