code: public static <T> T nullable(Class<T> clazz) {
          AdditionalMatchers.or(isNull(), isA(clazz));
          return  (T) Primitives.defaultValue(clazz);
      }
docs: Argument that is either <code>null</code> or of the given type.
  
  <p>
  See examples in javadoc for {@link ArgumentMatchers} class
  </p>
  
  @param clazz Type to avoid casting
  @return <code>null</code>.