Optional
keyPatt: anyRemove the key. Throws if not found.
Optional
keyPatt: anyCheck 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.
Optional
keyPatt: anyOptional
keyPatt: anyGenerated using TypeDoc
Add the key to the set if it is not already there. Do nothing silently if already there. The key must be one allowed by this store. For example a scalar store only allows primitives and remotables.