fun <E : Any, T : Iterable<E?>> Assert<T>.all(assertionCreatorOrNull: (Assert<E>.() -> Unit)?): AssertionPlant<T> (source)Makes the assertion that the Assert.subject has at least one element and
that every element holds all assertions created by the assertionCreatorOrNull or that all elements are null
in case assertionCreatorOrNull is defined as null.
AssertionError - Might throw an AssertionError if the assertion made is not correct.
Return
This plant to support a fluent API.