code: @javax.annotation.Nonnull
      public java.util.Optional<net.morimekta.providence.model.FilePos> optionalValueStartPos() {
          return java.util.Optional.ofNullable(mValueStartPos);
      }
docs: Note the start of the default value in the parsed thrift file, this can be used
  for making more accurate exception / parse data from the const parser.
  
  @return Optional of the <code>value_start_pos</code> field value.