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: stream.rs
    path of file: ./repos/Symphonia/symphonia-format-isomp4/src
    
    the code of the file until where you have to start completion: // Symphonia
// Copyright (c) 2019-2022 The Project Symphonia Developers.
//
// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this
// file, You can obtain one at https://mozilla.org/MPL/2.0/.
use symphonia_core::errors::{decode_error, Error, Result};

use crate::atoms::{stsz::SampleSize, Co64Atom, MoofAtom
    
    fn ts_sample(&self, track_num: usize, ts: u64) -> Result<Option<u32>> {
        // Get the track fragment associated with track_num.
        let traf = match self.try_get_traf(track_num) {
            Some(traf) => traf,
            None => return Ok(None),
        };

        let mut sample_num = self.seq[track_num].first_sample;
        let mut ts_accum = self.seq[track_num].first_ts;

        let default_dur = traf
            .tfhd
            .default_sample_duration
            .unwrap_or(self.mvex.trexs[track_num].default_sample_duration);

        for trun in traf.truns.iter() {
            // Get the total duration of this track run.
            let trun_dur = trun.total_duration(default_dur);

            // If the timestamp after the track run is greater than the desired timestamp, then the
            // desired sample must be in this run of samples.
            if ts_accum + trun_dur > ts {
                sample_num += trun.ts_sample(ts - ts_accum, default_dur);
                return Ok(Some(sample_num));
            }

            sample_num += trun.sample_count;
            ts_accum += trun_dur;
        }

        Ok(None)
    }