Check if object is an sqlalchemy model instance

I want to know how to know, given an object, if it is an instance of an sqlalchemy mapped model.

Normally, I would use isinstance(obj, DeclarativeBase). However, in this scenario, I do not have the DeclarativeBase class used available (since it is in a dependency project).

I would like to know what is the best practice in this case.

class Person(DeclarativeBase):
      __tablename__ = "Persons"

p = Person()

print isinstance(p, DeclarativeBase)
#prints True

#However in my scenario, I do not have the DeclarativeBase available
#since the DeclarativeBase will be constructed in the depending web app
#while my code will act as a library that will be imported into the web app
#what are my alternatives?