just-the-docs/_sass/support/mixins/_layout.scss

// Media query

// Media query mixin
// Usage:
// @include mq(md) {
//   ..medium and up styles
// }
@mixin mq($name) {
  // Retrieves the value from the key
  $value: map-get($media-queries, $name);

  // If the key exists in the map
  @if $value {
    // Prints a media query based on the value
    @media (width >= rem($value)) {
      @content;
    }
  } @else {
    @warn "No value could be retrieved from `#{$media-query}`. Please make sure it is defined in `$media-queries` map.";
  }
}

// Responsive container

@mixin container {
  padding-right: $gutter-spacing-sm;
  padding-left: $gutter-spacing-sm;

  @include mq(md) {
    padding-right: $gutter-spacing;
    padding-left: $gutter-spacing;
  }
}