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: source_map.rs
    path of file: ./repos/turbo/crates/turbopack-core/src/reference
    
    the code of the file until where you have to start completion: use anyhow::Result;
use turbo_tasks::{ValueToString, Vc};
use turbo_tasks_fs::{FileSystemEntryType, FileSystemPath};

use super::ModuleReference;
use crate::{
    fil
    
    async fn generate_source_map(&self) -> Result<Vc<OptionSourceMap>> {
        let Some(file) = self.get_file().await else {
            return Ok(Vc::cell(None));
        };
        let source_map = SourceMap::new_from_file(file).await?;
        Ok(Vc::cell(source_map.map(|m| m.cell())))
    }