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: perf_event.rs
    path of file: ./repos/youki/crates/libcgroups/src/v1
    
    the code of the file until where you have to start completion: use crate::common::{ControllerOpt, WrappedIoError};
use std::path::Path;

use super::controller::Controller;

pub struct PerfEvent {}

impl Controller for PerfEvent {
    type Error = Wra
    
    fn test_add_task() {
        let (tmp, procs) = setup(CGROUP_PROCS);
        let pid = Pid::from_raw(1000);

        PerfEvent::add_task(pid, tmp.path()).expect("apply perf_event");

        let content = fs::read_to_string(procs)
            .unwrap_or_else(|_| panic!("read {CGROUP_PROCS} file content"));
        assert_eq!(content, "1000");
    }