Sqla-history not able to handle `after_flush_postexec` hook

[indiVar0508]

When adding after_flush_postexec hook for modifying some values in DB after flush, the operation type is messed up

Code that reproduces this issue

import datetime
from sqlalchemy import Column, ForeignKey, Integer, DateTime, Table, create_engine, func, String, event
from sqlalchemy.orm import sessionmaker, relationship, configure_mappers, declarative_base
from sqlalchemy_history import make_versioned, version_class

make_versioned(user_cls=None)

Base = declarative_base()


book_author_table = Table(
    'book_author',
    Base.metadata,
    Column('book_id', Integer, ForeignKey('book.id'), primary_key=True, nullable=False),
    Column('author_id', Integer, ForeignKey('author.id'), primary_key=True, nullable=False),
    Column('created_date', DateTime, nullable=False, server_default=func.current_timestamp(), default=datetime.datetime.utcnow),
)


class Book(Base):
    __tablename__ = 'book'
    __versioned__ = {}

    id = Column(Integer, primary_key=True, autoincrement=True)
    name = Column(String(20), nullable=False)
    authors = relationship('Author', secondary=book_author_table, back_populates='books')


class Author(Base):
    __tablename__ = 'author'
    __versioned__ = {}

    id = Column(Integer, primary_key=True, autoincrement=True)
    name = Column(String(20), nullable=False)
    books = relationship('Book', secondary=book_author_table, back_populates='authors')

configure_mappers()
engine = create_engine('sqlite:///temp.db', echo=False)

# Create all tables
Base.metadata.drop_all(bind=engine)
Base.metadata.create_all(bind=engine)

# Create a session
session = sessionmaker()
session.configure(bind=engine)
db = session()

lotr = Book(name='Lord of the rings')
tolkien = Author(name='JRR Tolkien', books=[lotr])

@event.listens_for(session, 'after_flush_postexec')
def after_flush_postexec(session, flush_context):
    if tolkien.name != "yoyoyoyoyo":
        tolkien.name = "yoyoyoyoyo"
        new_user = Author(name='JRR Tolkien', books=[lotr])
        db.add(new_user)

db.add(lotr)
db.add(tolkien)
db.commit()

print(db.query(version_class(Author)).all())  
# >> [AuthorVersion(id=1, transaction_id=1, operation_type=1), AuthorVersion(id=2, transaction_id=1, operation_type=0)] 
# Author with id =1 should have operation_type as 1 but it is 0
tolkien.name = "yoyoyoyoyo1"
db.add(lotr)
db.add(tolkien)
db.commit()

print(db.query(version_class(Author)).all())
# >> [AuthorVersion(id=1, transaction_id=1, operation_type=1), AuthorVersion(id=2, transaction_id=1, operation_type=0), AuthorVersion(id=1, transaction_id=2, operation_type=1), AuthorVersion(id=3, transaction_id=2, operation_type=0)]
# first record should have operation type as 0