use std::collections::BTreeMap;
use crate::Map;
impl<K, V, C> Map<K, V> for BTreeMap<K, C>
where
K: Eq + Ord + std::hash::Hash,
C: Default + Extend<V>,
{
fn insert(&mut self, key: K, value: V) {
self.entry(key).or_default().extend(std::iter::once(value));
}
}