code: function (element, number) {
  			if (element.tagName !== 'PRE' || !element.classList.contains(PLUGIN_NAME)) {
  				return;
  			}
  
  			var lineNumberRows = element.querySelector('.line-numbers-rows');
  			var lineNumberStart = parseInt(element.getAttribute('data-start'), 10) || 1;
  			var lineNumberEnd = lineNumberStart + (lineNumberRows.children.length - 1);
  
  			if (number < lineNumberStart) {
  				number = lineNumberStart;
  			}
  			if (number > lineNumberEnd) {
  				number = lineNumberEnd;
  			}
  
  			var lineIndex = number - lineNumberStart;
  
  			return lineNumberRows.children[lineIndex];
  		}
docs: Get node for provided line number
  @param {Element} element pre element
  @param {Number} number line number
  @return {Element|undefined}