abstract fun <T> newCollectingPlantNullable(subjectProvider: () -> T): CollectingAssertionPlantNullable<T>Creates a CollectingAssertionPlantNullable which is intended to be used as receiver object in lambdas to collect created Assertions inside the lambda.
Notice, that the plant might not provide a CollectingAssertionPlantNullable.subject in which case it throws a PlantHasNoSubjectException if subject is accessed.
subjectProvider - The function which will either provide the subject for this plant or throw an
PlantHasNoSubjectException in case it cannot provide it. A CollectingAssertionPlant should evaluate the
subjectProvider only once.
Return
The newly created assertion plant.