<===> options.yml
---
:todo:
- sass/libsass#1224
<===> input.scss
@media all and (max-width: 768px) {
  @media only screen {
    a { b: c; }
  }
}

<===> output.css
@media only screen and (max-width: 768px) {
  a {
    b: c;
  }
}