I got problem with serialization

I got a problem with serialization. Most of the project classes aren't signed as Serializable (system.serializable). I can't serialize classes without using reflection. I can't even inherit these.

No files or tests are named. Start by inspecting the project classes involved in serialization and how they are declared, then check the project’s existing serialization expectations. Done means the relevant classes support serialization and inheritance without reflection, with verification added where the project provides a test path.

Written by the indexing model from the issue text.