code: function renameNodes(nodes, sourcePath, opts, mappings) {
    return nodes.map(function(node) {
      // Process CSS node
      if (node.type === 'class') {
        // Process "class" node
        var orgValue = node.value,
            newValue = renameClassNode(node.value, sourcePath, opts);
        // Edit node and store mapping of classname renaming
        node.value = mappings[orgValue] = newValue;
      } else if (node.type === 'pseudo' && node.value === ':not') {
        // Process ":not([selector])" pseudo node
        renameNodes(node.nodes, sourcePath, opts, mappings);
      } else if (node.type === 'selector') {
        // Rename selector nodes
        renameNodes(node.nodes, sourcePath, opts, mappings)
      }
    });
  }
docs: Renames all classnames in css nodes
  @param nodes css nodes
  @param sourcePath Source file's path
  @param opts Options object
  @param mappings Classname to renamed classname mappings repository
  @return {*} Renamed css nodes