The ViewCube example uses the non existent "back" event to demonstrate the ViewCuvbe interaction at [L89-91](https://github.com/ThatOpen/engine_ui-components/blob/bf95cc2031ba98ea3c78bbd6c33341c5ed3ccb1c/packages/obc/src/core/ViewCube/example.ts#L89-L91). Also there is a empty code block in the documentation because of an old (?) duplicate explanation at [L69-71](https://github.com/ThatOpen/engine_ui-components/blob/bf95cc2031ba98ea3c78bbd6c33341c5ed3ccb1c/packages/obc/src/core/ViewCube/example.ts#L69-L71)
