Entry
Parameter object to express a Group with a single identification lambda.
In case null is used for the identification lambda then it is expected that the corresponding entry is null as well.
Use the function entry { ... } to create this representation.
Parameters
assertionCreatorOrNull
The identification lambda identifying the entry where an entry is considered to be identified if it holds all Assertions the lambda creates. In case it is defined as null, then an entry is identified if it is null as well.