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: graph.rs
    path of file: ./repos/rain/rain_server/src/server/graph
    
    the code of the file until where you have to start completion: use rain_core::types::*;
use std::collections::HashMap;

use super::{ClientRef, DataObjectRef, GovernorRef, SessionRef, TaskRef};

#[derive(Clone, Default)]
pub struct Graph {
    /// Contained objects
    pub(in super::super) governors: HashMap<GovernorId, GovernorRef>,
    pub(in super::super) tasks: HashMap<TaskId, TaskRef>,
    pub(in super::super) obj
    
    fn graph_create_delete() {
        let g = create_test_graph(4, 2, 3, 10, 20);

        assert!(!g.objects.is_empty());
        assert!(!g.governors.is_empty());

        //let client_rcs: Vec<_> = g.clients.values().map(|x| x.clone()).collect();
        //let governor_rcs: Vec<_> = g.governors.values().map(|x| x.clone()).collect();

        // FIXME!
        //for c in client_rcs { c.delete(&mut g); }
        //for w in governor_rcs { w.delete(&mut g); }

        assert!(g.clients.is_empty());
        assert!(g.governors.is_empty());
        assert!(g.tasks.is_empty());
        assert!(g.objects.is_empty());
        assert!(g.sessions.is_empty());
    }