private static TypeName getClassTypeName(
        ClassName className, List<TypeVariableName> typeVariableNames) {
      return typeVariableNames.isEmpty()
          ? className
          : ParameterizedTypeName.get(className, typeVariableNames.toArray(new TypeName[] {}));
    }
Adds type parameters to the given {@link ClassName}, if available.
value/src/main/java/com/google/auto/value/extension/serializable/processor/SerializableAutoValueExtension.java