pub fn write(&self, toml: &str, mut out: impl io::Write) -> io::Result<()> {
        write!(out, "{}", &self.contents[..self.start_offset])?;
        write!(out, "{}", toml)?;
        write!(out, "{}", &self.contents[self.end_offset..])
    }
Writes out the full contents, including the provided TOML, to the given writer.
tools/hakari/src/cargo_toml.rs