code: function normalizePair(pair, resolver, dirname) {
    var options = void 0;
    var value = pair;
    if (Array.isArray(pair)) {
      if (pair.length > 2) {
        throw new Error("Unexpected extra options " + (0, _stringify2.default)(pair.slice(2)) + ".");
      }
  
      var _pair = (0, _slicedToArray3.default)(pair, 2);
  
      value = _pair[0];
      options = _pair[1];
    }
  
    var filepath = null;
    if (typeof value === "string") {
      var _resolver = resolver(value, dirname);
  
      filepath = _resolver.filepath;
      value = _resolver.value;
    }
  
    if (!value) {
      throw new Error("Unexpected falsy value: " + String(value));
    }
  
    if ((typeof value === "undefined" ? "undefined" : (0, _typeof3.default)(value)) === "object" && value.__esModule) {
      if (value.default) {
        value = value.default;
      } else {
        throw new Error("Must export a default export when using ES6 modules.");
      }
    }
  
    if ((typeof value === "undefined" ? "undefined" : (0, _typeof3.default)(value)) !== "object" && typeof value !== "function") {
      throw new Error("Unsupported format: " + (typeof value === "undefined" ? "undefined" : (0, _typeof3.default)(value)) + ". Expected an object or a function.");
    }
  
    if (options != null && (typeof options === "undefined" ? "undefined" : (0, _typeof3.default)(options)) !== "object") {
      throw new Error("Plugin/Preset options must be an object, null, or undefined");
    }
  
    return { filepath: filepath, value: value, options: options };
  }
docs: Given a plugin/preset item, resolve it into a standard format.