code: private <T> T assertNotNull(T value, Supplier<String> message) {
      Assert.notNull(value, message);
      return value;
    }
docs: Assert the given {@link Object value} is not {@literal null}.
  
  @param <T> {@link Class type} of the {@link Object value}.
  @param value {@link Object} to evaluate.
  @param message {@link Supplier} containing the message used in the {@link IllegalArgumentException}.
  @return the given {@link Object value} if not {@literal null}.
  @throws IllegalArgumentException with {@link Supplier message} if the {@link Object value} is {@literal null}.
  @see java.util.function.Supplier