    "Given a list of iterable objects, return a new sequence
     of all elements of the all given objects. If there are
     no arguments, or if none of the arguments contains any
     elements, return the empty sequence."
    see (`class SequenceBuilder`)
    shared Element[] concatenate<Element>(
            "The iterable objects to concatenate."
            {Element*}* iterables) =>
                    [ for (it in iterables) for (val in it) val ];