Checks that this iterable has only one element, and returns that element.

Throws aStateError ifthis is empty or has more than one element.This operation will not iterate past the second element.

Implementation

Plugin get single {  int len = this.length;  if (len == 1) {    return JS('Plugin', '#[0]', this);  }  if (len == 0) throw new StateError("No elements");  throw new StateError("More than one element");}