docs: @Nonnull
    public FineUploader5Chunking setParamNamePartIndex (@Nonnull @Nonempty final String sParamNamePartIndex)
    {
      ValueEnforcer.notEmpty (sParamNamePartIndex, "ParamNamePartIndex");
      m_sChunkingParamNamesPartIndex = sParamNamePartIndex;
      return this;
    }