Select Option Groups

Problem/Motivation

I want to make a form with a select, with option groups

Steps to reproduce

heres my yaml code (found out how to do this from other issues in this queue)

test:
  '#type': select
  '#title': Test
  '#options':
    'Opt Group 1': 
    'something else': 'something else'
    'another thing': 'another thing'
    'Opt Group 2': 
    'yet something else': 'yet something else'
    'yet another thing': 'yet another thing'
  '#empty_option': 'please select'

however when I save it it becomes (I guess the parser is doing this).

test:
  '#type': select
  '#title': Test
  '#options':
    'Opt Group 1': null
    'something else': 'something else'
    'another thing': 'another thing'
    'Opt Group 2': null
    'yet something else': 'yet something else'
    'yet another thing': 'yet another thing'
  '#empty_option': 'please select'

And then the Opt Group 1 (&2) become standard options.. am I missing something?