keys property
The keys of the values of an app of the matrix, each with the module that gives the app the key; none for an app whose modules read no values.
The report of the tests of a matrix tool (appTestsReport) names, for each key that a test gives an app a value of, its module, so that the checks of the repository find a test that gives values for the keys of a module that it does not know.
Implementation
final Map<String, ModuleId> Function(MatrixApp app) keys;