[Python] Sqlalchemy CASCADE delete mode is not applied [duplicate]

I have a sqlalchemy table, the table created fine, but I don't see CASCADE delete mode in solution column. I am checking like this ( confdeltype is 'a' not 'c'):

dbname=# select connamespace, conname, c.relname as child_table, p.relname as parent_table, confdeltype from pg_constraint join pg_class c on c.oid=conrelid join pg_class p on p.oid=confrelid;
connamespace | conname | child_table | parent_table | confdeltype
--------------+--------------------------+-------------+--------------+-------------
2200 | tasks_files_task_id_fkey | tasks_files | tasks | a
2200 | solutions_task_id_fkey | solutions | tasks | a
(2 rows)


Table:

class Task(Base):
__tablename__ = 'tasks'

id = Column(String, unique=True, nullable=False, primary_key=True)
...
files: Mapped[List["TaskFile"]] = relationship(cascade="all, delete")
solution: Mapped[List["Solution"]] = relationship(cascade="all, delete")
output_topic = Column(String)


The table looks like this in psql:

dbname=# \d+ tasks
Table "public.tasks"
Column | Type | Collation | Nullable | Default | Storage | Stats target | Description
--------------------+-----------------------------+-----------+----------+---------+----------+--------------+-------------
id | character varying | | not null | | extended | |
external_id | character varying | | not null | | extended | |
rq_id | character varying | | not null | | extended | |
...
Indexes:
"tasks_pkey" PRIMARY KEY, btree (id)
Referenced by:
TABLE "solutions" CONSTRAINT "solutions_task_id_fkey" FOREIGN KEY (task_id) REFERENCES tasks(id)
TABLE "tasks_files" CONSTRAINT "tasks_files_task_id_fkey" FOREIGN KEY (task_id) REFERENCES tasks(id)
Access method: heap

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