code: public static <T> TypeSerializer<T> wrap(
  		@Nonnull TypeSerializer<T> originalSerializer, boolean padNullValueIfFixedLen) {
  		return originalSerializer instanceof NullableSerializer ?
  			originalSerializer : new NullableSerializer<>(originalSerializer, padNullValueIfFixedLen);
  	}
docs: This method wraps the {@code originalSerializer} with the {@code NullableSerializer} if not already wrapped.
  
  @param originalSerializer     serializer to wrap and add {@code null} support
  @param padNullValueIfFixedLen pad null value to preserve the fixed length of original serializer
  @return wrapped serializer which supports {@code null} values