code: function validate( opts, options ) {
  	if ( !isPlainObject( options ) ) {
  		return new TypeError( 'invalid argument. Options must be an object. Value: `' + options + '`.' );
  	}
  	if ( hasOwnProp( options, 'TODO' ) ) {
  		opts.TODO = options.TODO;
  		if ( !isPlainObject( opts.TODO ) ) {
  			return new TypeError( 'invalid option. `TODO` option must be a TODO. Option: `' + opts.TODO + '`.' );
  		}
  	}
  	return null;
  }
docs: MAIN // 
  Validates function options.
  
  @private
  @param {Object} opts - destination object
  @param {Options} options - function options
  @returns {(Error|null)} null or an error object
  
  @example
  var opts = {};
  var options = {};
  var err = validate( opts, options );
  if ( err ) {
  throw err;
  }