iterator
 Platform and version requirements: Native (1.3) 
fun iterator(): MutableIterator<E>
 Platform and version requirements: JS (1.1) 
open fun iterator(): MutableIterator<E>
Returns an iterator over the elements of this object.
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Licensed under the Apache License, Version 2.0.
    https://kotlinlang.org/api/latest/jvm/stdlib/kotlin.collections/-hash-set/iterator.html