code: function _isAtruleDescendant(node) {
    let { parent } = node;
    let descended = false;
  
    while (parent && parent.type !== 'root') {
      if (parent.type === 'atrule') {
        descended = parent.params;
      }
      ({ parent } = parent);
    }
    return descended;
  }
docs: Private: checks if a node is a decendant of an [AtRule](http://api.postcss.org/AtRule.html).
  
  * `node` {Object} PostCSS Node to check.
  
  Returns {Boolean} of false, or {String} of AtRule params if true.