Abstract pexpect.SpawnBase has no send/sendline/write/writelines stubs

The actual implementation of pexpect.SpawnBase does not contain these functions but it is an abstract class and all children have these write methods.

Since almost all interesting pexpect code does some form of writing it is impractical to use SpawnBase as an annotation. The only viable solution seem to be annotating with PopenSpawn or maybe an union if you actually want to be generic?

Perhaps it would be acceptable to add these stubs to SpawnBase despite what is written in the implementation.

Individua lo stub SpawnBase in typeshed e confrontalo con gli stub figlio che definiscono send, sendline, write e writelines. Controlla i test di typing pertinenti oppure esegui i test di type-checking del repository per confermare che le annotazioni di SpawnBase espongano questi metodi senza compromettere le implementazioni esistenti.