title: Check if SASS parent selector exists. Is it possible
body: <p>I have a question. So in a mixing I am making a reference to the parent selector "&amp;". This works as long as the mixin is not nested. Is there a way to to detect if the mixing is being used in a non nested scenario, or to check if "&amp;" is null?</p>
  
  <p>This works when the mixin call is not nested</p>
  
  <pre><code>=myresponsiveMixin($media)
    @if $media == small {
      @media only screen and (max-width: $break-small)
         @content
    @else if $media == medium
      @media only screen and (min-width: $break-small + 1) and (max-width: $break-large - 1)
         @content
  </code></pre>
  
  <p>This works great when the mixin call is nested, but will not resolve '&amp;' when not nested</p>
  
  <pre><code> =myresponsiveMixin($media)
        @if $media == small {
          @media only screen and (max-width: $break-small)
             .classInHTMLToAllowMediaQueries &amp;
                 @content
        @else if $media == medium
          @media only screen and (min-width: $break-small + 1) and (max-width: $break-large - 1)
             .classInHTMLToAllowMediaQueries &amp;
                 @content
  </code></pre>
  
  <p>So the question is, if there is a way to be able to check the value of parent selector "&amp;", so I can cover all bases in a single mixin?  </p>