Function execute 

pub fn execute(
    scene: Arc<RwLock<Scene>>,
    pipeline: Pipeline,
    gback: impl Backend,
)

Construct a covalent context from the given backend, then executes the application defined by this Covalent context. Only create a single context during the lifetime of your application, and only create this context on the main thread!

You should never need to interact with the context manually - it is all handled by the active graphics backend.