Create creates a new Todo and stores it.

Delete removes a task from the task store, given its key.

Get returns the Todo specified by a given key.

GetAll returns all Todos in the store.

GetFiltered returns Todos in the store that match a predicate.

Init creates the task store (unless one exists) and guarantees buckets.

Update performs an update action on a Task specified by a given key.

Todo represents a task and its associated completion status.

FilterFn defines the signature for a predicate function to be used with GetFiltered().

UpdateFn defines the signature for a function that updates a task.