Issue #3518967 by quadrexdev, joachim: incorrect @return docs for...

   *   The machine name of an element type plugin.

   *

   * @return array

   *   An associative array describing the element types being defined. The

   *   array contains a sub-array for each element type, with the

   *   machine-readable type name as the key. Each sub-array has a number of

   *   possible attributes:

   *   - #input: boolean indicating whether or not this element carries a value

   *   An associative array describing the element type being defined. The

   *   array has a number of possible attributes:

   *   - #input: boolean indicating whether this element carries a value

   *     (even if it's hidden).

   *   - #process: array of callback functions taking $element, $form_state,

   *     and $complete_form.