code: function( block, linesToHighlight ) {
  
  			linesToHighlight = linesToHighlight || block.getAttribute( 'data-line-numbers' );
  
  			if( typeof linesToHighlight === 'string' && linesToHighlight !== '' ) {
  
  				linesToHighlight.split( ',' ).forEach( function( lineNumbers ) {
  
  					// Avoid failures becase of whitespace
  					lineNumbers = lineNumbers.replace( /\s/g, '' );
  
  					// Ensure that we looking at a valid slide number (1 or 1-2)
  					if( /^[\d-]+$/.test( lineNumbers ) ) {
  
  						lineNumbers = lineNumbers.split( '-' );
  
  						var lineStart = lineNumbers[0];
  						var lineEnd = lineNumbers[1] || lineStart;
  
  						[].slice.call( block.querySelectorAll( 'table tr:nth-child(n+'+lineStart+'):nth-child(-n+'+lineEnd+')' ) ).forEach( function( lineElement ) {
  							lineElement.classList.add( 'highlight-line' );
  						} );
  
  					}
  
  				} );
  
  			}
  
  		}
docs: Visually emphasize specific lines within a code block.
  This only works on blocks with line numbering turned on.
  
  @param {HTMLElement} block a <code> block
  @param {String} [linesToHighlight] The lines that should be
  highlighted in this format:
  "1" 		= highlights line 1
  "2,5"	= highlights lines 2 & 5
  "2,5-7"	= highlights lines 2, 5, 6 & 7