IsolateSetup typedef
        IsolateSetup =
     FutureOr<void>  Function()
    
    
Signature of a function that can perform setup work on the isolate before opening the database.
This could be used to override libraries. For example:
open.overrideFor(OperatingSystem.android, openCipherOnAndroid)
Implementation
typedef IsolateSetup = FutureOr<void> Function();