Return a value for the key. Throws if not found.
Check if a key exists. The key can be any JavaScript value, though the answer will always be false for keys that cannot be found in this store.
Initialize the key only if it doesn't already exist. The key must be one allowed by this store. For example a scalar store only allows primitives and remotables.
Set the key. Throws if not found.
Remove the key. Throws if not found.