val <K : Any> Assert<Pair<K, *>>.first: Assert<K>Creates an AssertionPlant for the Assert.subject's property first so that further fluent calls are assertions about it.
Wrap it into Kotlin's apply if you want to make subsequent assertions on the current subject or use the overload which expects an assertionCreator lambda where sub assertions are evaluated together (form an assertion group block).
Return
The newly created AssertionPlant.
fun <K : Any, V> Assert<Pair<K, V>>.first(assertionCreator: Assert<K>.() -> Unit): AssertionPlant<Pair<K, V>>Makes the assertion that the Assert.subject's property first holds all assertions the given assertionCreator might create for it.
AssertionError - Might throw an AssertionError if a created Assertions (by calling assertionCreator)
does not hold.
IllegalArgumentException - in case the given assertionCreator did not create a single assertion.
Return
This plant to support a fluent API.