Invariant means that neither subtype nor supertype can be accepted, the type has to be exactly that which is declared.

- `Anything`
  - `Object`
    - `Basic` ...and other supertypes
      - `invariant` ...and other supertypes

- `invariant`
  - `Basic`
    - `Identifiable`
    - `Object`
      - `Anything`
  - `Variance`

no subtypes hierarchy

Attributes
`string` | Source Code `shared actual String string` A developer-friendly string representing the instance. Concatenates the name of the concrete class of the instance with the `hash` of the instance. Subclasses are encouraged to refine this implementation to produce a more meaningful representation. Refines `Object.string`

Inherited Attributes
Attributes inherited from: `Object` `hash`, `string`

Inherited Methods
Methods inherited from: `Object` `equals()`