Type Alias Once 

pub type Once = OnceCell<(), NoBlock>;

A synchronization primitive which can be used to run a one-time global initialization.

This type does not permit any (potentially) blocking operations, only their respective non-blocking counterparts and is thus #[no_std] compatible.

For the API of this type alias, see the generic OnceCell type. This is a specialization with T = ().

Aliased Type

pub struct Once { /* private fields */ }