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: prover_task_runner.rs
    path of file: ./repos/diem/language/move-prover/boogie-backend/src
    
    the code of the file until where you have to start completion: // Copyright (c) The Diem Core Contributors
// SPDX-License-Identifier: Apache-2.0

//! Prover task runner that runs multiple instances of the prover task and returns
//! as soon as the fastest instance finishes.

use crate::options::B
    
    fn init(&mut self, num_instances: usize) -> Vec<Self::TaskId> {
        // If we are running only one Boogie instance, use the default random seed.
        if num_instances == 1 {
            return vec![self.options.random_seed];
        }
        let mut rng = rand::thread_rng();
        // Otherwise generate a list of random numbers to use as seeds.
        (0..num_instances)
            .map(|_| rng.gen::<u8>() as usize)
            .collect()
    }