singleOrElse method
Emits the single element of this Observable, or evaluates the tooFew
callback if there was no element, or evaluates the tooMany
callback if
there was more than 1 element.
Implementation
Observable<T> singleOrElse({
required Map0<T> tooFew,
required Map0<T> tooMany,
}) => SingleObservable<T>(this, tooFew, tooMany);