Function write_tar 

pub fn write_tar<W>(
    writer: W,
    case: &Case,
    bus: &[Bus],
    gen: &[Gen],
    branch: &[Branch],
    gencost: &[GenCost],
    dcline: &[DCLine],
    readme: Option<String>,
    license: Option<String>,
) -> Result<W>
where
    W: Write,