The SlackAPIFileOperator is not straight forward and it might be better to add an example DAG to demonstrate the usage.

tests/providers/slack/operators/test_slack.py
return SlackAPIPostOperator(
            task_id='slack',
            username=self.test_username,
            token=test_token,
            slack_conn_id=test_slack_conn_id,
            channel=self.test_channel,
            text=self.test_text,
            icon_url=self.test_icon_url,
            attachments=self.test_attachments,
            blocks=self.test_blocks,
            api_params=test_api_params,
        )
    def test_init_with_valid_params(self):