Figured it out:
connection_string: str = "sqlite:///:memory:"
engine = create_engine(connection_string)
session = Session(bind=engine)
print(type(engine)) # sqlalchemy.engine.base.Engine
print(type(session)) # sqlalchemy.orm.session.Session
Thus, type hinting is achieved the following way for example:
from sqlalchemy.engine.base import Engine
def test_func(engine: Engine):
pass