code: @NullSafe
    protected String valueOf(String value) {
      return ("null".equalsIgnoreCase(String.valueOf(value).trim()) ? null : value);
    }
docs: Returns {@literal null} for a {@literal "null"} {@link String} value or simply returns the {@link String} value.
  The {@link String} value is safely trimmed before evaluation.
  
  @param value {@link String} value to evaluate.
  @return a {@literal null} for a {@literal "null"} {@link String} value.
  @see java.lang.String