You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: slice.rs
    path of file: ./repos/qsv/src/cmd
    
    the code of the file until where you have to start completion: static USAGE: &str = r#"
Returns the rows in the range specified (starting at 0, half-open interval).
The range does not include headers.

If the start of the range isn't specified, then the slice s
    
    fn range(&self) -> Result<(usize, usize), String> {
        let mut start = None;
        if let Some(start_arg) = self.flag_start {
            if start_arg < 0 {
                start = Some(
                    (util::count_rows(&self.rconfig()).unwrap() as usize)
                        .abs_diff(start_arg.unsigned_abs()),
                );
            } else {
                start = Some(start_arg as usize);
            }
        }
        util::range(start, self.flag_end, self.flag_len, self.flag_index)
    }