code: function uncommonAttributes(node, selectorData) {
  	let retVal = [];
  	let attData = selectorData.attributes;
  	let tagData = selectorData.tags;
  
  	if (node.hasAttributes()) {
  		Array.from(axe.utils.getNodeAttributes(node))
  			.filter(filterAttributes)
  			.forEach(at => {
  				const atnv = getAttributeNameValue(node, at);
  
  				if (atnv && attData[atnv] < tagData[node.nodeName]) {
  					retVal.push({
  						name: atnv,
  						count: attData[atnv],
  						species: 'attribute'
  					});
  				}
  			});
  	}
  	return retVal.sort(countSort);
  }
docs: Given a node and the statistics on attribute frequency on the page,
  return all its uncommon attribute data sorted in order of decreasing uniqueness
  @param {Element} node			The node
  @param {Object} attData		The map of attributes to counts
  @return {Array}						The sorted array of uncommon attribute data