@observes does not detect changes in columns inherited from a mixin

[FeehGb]

Description:

I am encountering an issue when using @observes("dt_alteracao") in a model that inherits dt_alteracao from a TimestampMixin. The observer correctly detects changes when the column is modified directly in the model, but it does not trigger when the change comes from the mixin.

Code to reproduce:

from datetime import datetime
from sqlalchemy import Column, TIMESTAMP, text
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy_utils import observes

Base = declarative_base()

class TimestampMixin:
    __abstract__ = True

    __datetime_func__ = text("CURRENT_TIMESTAMP")

    dt_inclusao = Column("dt_inclusao", TIMESTAMP(timezone=False), server_default=__datetime_func__, nullable=False)
    dt_alteracao = Column(
        "dt_alteracao",
        TIMESTAMP(timezone=False),
        server_default=__datetime_func__,
        onupdate=__datetime_func__,
        nullable=False,
    )

class MyModel(Base, TimestampMixin):
    __tablename__ = "my_model"
    id = Column("id", TIMESTAMP(timezone=False), primary_key=True)

    @observes("dt_alteracao")
    def usuario_inclusao_alteracao_observer(self, value: datetime):
        print(f"Observer triggered: {value}")

Expected Behavior:

The observer should be triggered when dt_alteracao is updated, regardless of whether the column comes from the mixin or is defined directly in the model.

Observed Behavior:

The observer is only triggered when dt_alteracao is changed within the model itself, but not when the change originates from the mixin.

Environment:

• Python version: 3.12
• SQLAlchemy version: 2.0.36
• SQLAlchemy-Utils version: 0.41.2

Is this the expected behavior, or is there a way to ensure that changes to mixin-inherited columns are observed?