/// Check whether the map is empty.
Check whether the map is empty.
Check whether the map is empty .
pub fn is_empty(self) -> bool {
        match self {
            Map(None) => true,
            Map(Some(_)) => false,
        }
    }
pub fn is_empty ( self ) -> bool { match self { Map ( None ) => true , Map ( Some ( _ ) ) => false , } }
Check whether the map is empty.
Check whether the map is empty .
self