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: tabs.rs
    path of file: ./repos/delta/src/utils
    
    the code of the file until where you have to start completion: use unicode_segmentation::UnicodeSegmentation;

#[derive(Debug, Clone)]
pub struct TabCfg {
    replacement: String,
}

impl TabCfg {
    pub fn new(width: usize) -> Self {
        TabCfg {
            replacement: " ".repeat(width),
        }
    }
    pub fn width(&self) -> usize {
        self.replacement.len()
    }
    pub fn replace(&self) -> bool {
        !self.replacement.is_empty()
    }
}

/// Expand tabs as spaces.
pub fn expand(line: &str, tab_cfg: &TabCfg) -> String {
 
    
pub fn remove_prefix_and_expand(prefix: usize, line: &str, tab_cfg: &TabCfg) -> String {
    let line_bytes = line.as_bytes();
    // The to-be-removed prefixes are almost always ascii +/- (or ++/ +/.. for merges) for
    // which grapheme clusters are not required.
    if line_bytes.len() >= prefix && line_bytes[..prefix].is_ascii() {
        // Safety: slicing into the utf-8 line-str is ok, upto `prefix` only ascii was present.
        expand(&line[prefix..], tab_cfg)
    } else {
        let cut_line = line.graphemes(true).skip(prefix).collect::<String>();
        expand(&cut_line, tab_cfg)
    }
}