function _getPercentElement(targetElement) {
    var progressjsId = parseInt(targetElement.getAttribute('data-progressjs'));
    return document.querySelector('.progressjs-container > .progressjs-progress[data-progressjs="' + progressjsId + '"] > .progressjs-inner');  
  }
Get the progress bar element 

@api private
@method _getPercentElement
@param {Object} targetElement