single property
override
Checks that this iterable has only one element, and returns that element.
Throws a StateError if this
is empty or has more than one element.
This operation will not iterate past the second element.
Implementation
@override
E get single {
if (isEmpty) {
throw _noElements();
}
if (length > 1) {
throw _moreThanOneElement();
}
return elementAt(0);
}