How to add task list to existing DAG

I'm trying to automate the creation of batch pipelines from backend mySQLL to BiqQuery and I've ran into issue with my script.

It initialises a DAG with it's own class (DagCreator) and then passes it as a instance variable in my MySQLBatchPipelines class.

The tasks and the order of the tasks are contained in methods inside my MySQLBatchPipelines instance.

How would I add those tasks and the tasks list to my existing DAG?

Here's some example code so you understand my query:

class DagCreator:

    def __init__(
        self,
        dag_id,
        start_date,
        time_delay: int
    ):
        self.dag_id = dag_id,
        self.start_date = start_date,
        self.time_delay = time_delay

        print(self.dag_id)

    def DagToReturn(self):
        args = {
            'owner': 'Data Lake',
            'depends_on_past': True,
            'start_date': self.start_date,
            'email_on_failure': False,
            'email_on_retry': False,
            'on_failure_callback': 'failed_dag_slack_alert',
            'retries': 0,
            'max_active_runs': 1,
            'max_file_size': int(50e6)
        }
        dag_to_return = DAG(
            dag_id=f'{self.dag_id}_batch',
            schedule_interval=f'{self.time_delay} * * *',
            concurrency=4,
            default_args=args
        )
        return dag_to_return

dag = DagCreator('table_name', dt.datetime(2022, 1, 15), 7)
dag_returned = dag.DagToReturn()
dag_returned

This is the second class and it's methods:

class MySQLBatchPipeline:
    '''
    Class to generate MySQL batch pipelines that store CSV's 
    in GCS then import them into BigQuery
    '''
    export_format='CSV' 

    def __init__(
        self,
        dag,
    ....

    # lots of methods that return tasks like these
    def uk_source_table_extract_task(self):
        uk_source_table_extract_task = MySqlToGoogleCloudStorageOperator(
            sql=self.queries['new_rows_batch_query'], # <--- needs testing
            bucket=self.gcs_bucket,
            filename=self.extract_gcs_path,
            approx_max_file_size_bytes=MAX_FILE_SIZE, # <-- is max_file_size necc? is in dag arg's is it necc here
            mysql_conn_id=self.mysql_connection_id,
            export_format=self.export_format,
            google_cloud_storage_conn_id=self.gcs_connection_id,
            params={
                'export_format': self.export_format,
                'country': 'uk',
                'time_delay': self.time_delay
            },
            task_id='uk_source_table_extract_task',
            dag=self.dag
      return uk_expected_stg_row_count_extract_task


    # this the the workflow I want to add to the existing DAG I've passed a instance attribute
        def uk_workflow(self):
            uk_source_table_extract_task.set_downstream(
                [
                    uk_table_name_load_task,
                    uk_truncate_table_name_staging_task,
                    uk_expected_stg_row_count_extract_task
                ]
            )
            uk_truncate_table_name_staging_task.set_downstream(
            uk_table_name_load_task
            # etc etc until the final task

source https://stackoverflow.com/questions/70756217/how-to-add-task-list-to-existing-dag