If sqlhub.processConnection is set before a subclass of SQLObject is defined, then the _connection attribute of the new class will be ignored. This is, as far as I could find out, because of:
if connection and not hasattr(cls, '_connection'):
This creates a lot of confusion and, if I understood correctly, is not the intended behaviour either (citing from the documentation):
"If you have defined sqlhub.processConnection then this attribute can be omitted from your class and the sqlhub will be used instead. If you have several classes using the same connection that might be an advantage, besides saving a lot of typing."