code: function str(input) {
    if (!is('String', input)) return;
    return root[input] || (root.require || require)(input);
  }
docs: Check if `input` is a string and if so, either
  refer to the global scope or `require` it. Then
  call `loa` again in case the exported object
  is a function.
  
  @param {Mixed} input
  @api private