docs: function checkOptions(caps, key, optionType, setMethod) {
    let val = caps.get(key);
    if (val instanceof optionType) {
      throw new error.InvalidArgumentError(
          'Options class extends Capabilities and should not be set as key '
              + `"${key}"; set browser-specific options with `
              + `Builder.${setMethod}(). For more information, see the `
              + 'documentation attached to the function that threw this error');
    }
  }