Function siblings 

pub fn siblings(store: &impl ProcessStore, pid: u32) -> Vec<u32>

Get siblings of a PID (processes with the same parent).

Excludes the given pid itself.

use proc_tree::{DefaultStore, siblings, ProcessStore, ProcessInfo};

let store = DefaultStore::new(0);
store.insert_process(1, ProcessInfo::new("init".into(), "init".into(), "root".into(), 0, 1, 0));
store.insert_process(100, ProcessInfo::new("a".into(), "a".into(), "root".into(), 1, 100, 0));
store.insert_process(200, ProcessInfo::new("b".into(), "b".into(), "root".into(), 1, 200, 0));
store.insert_process(300, ProcessInfo::new("c".into(), "c".into(), "root".into(), 1, 300, 0));

let mut sibs = siblings(&store, 100);
sibs.sort();
assert_eq!(sibs, vec![200, 300]);
assert!(siblings(&store, 1).is_empty()); // init has no siblings