code: function preprocess(callback) {
  
  	var sheets = arrayFrom(styleSheets);
  
  	// Check removed stylesheets
  	processedSheets.forEach(function(newNode, node) {
  		// Original stylesheet has been deleted
  		if (sheets.indexOf(node.sheet) === -1) {
  			if (newNode && sheets.indexOf(newNode.sheet) !== -1 && newNode.parentNode) {
  				sheets.splice(sheets.indexOf(newNode.sheet), 1);
  				newNode.parentNode.removeChild(newNode);
  			}
  			processedSheets.delete(node);
  		}
  	});
  
  	var done = -1;
  	function step() {
  		done++;
  		if (done === sheets.length) {
  			callback();
  		}
  	}
  	sheets.forEach(function(sheet) {
  		preprocessSheet(sheet, step);
  	});
  	step();
  
  }
docs: Step 1: Preprocess all active stylesheets in the document
  
  Look for stylesheets that contain container queries and escape them to be
  readable by the browser, e.g. convert `:container(width >= 10px)` to
  `\:container\(width\>\=10px\)`
  
  @param {function()} callback