/// A reactive subscription to changes on a tree.
type Subscription<'k, 'v>;
/// Subscribe to changes on a tree, optionally filtering by key prefix.
val new: fn(?#prefix: ['k, null], t: Tree<'k, 'v>) -> Subscription<'k, 'v>;
/// Fires reactively when inserts occur on the subscription.
val on_insert: fn(sub: Subscription<'k, 'v>) -> Result<Array<{key: 'k, value: 'v}>, `DbErr(string)>;
/// Fires reactively when removes occur on the subscription.
val on_remove: fn(sub: Subscription<'k, 'v>) -> Result<Array<{key: 'k}>, `DbErr(string)>;