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
"footer_icon": "https://platform.slack-edge.com/img/default_application_icon.png",
                "ts": 123456789,
            }
        ]
        self.test_blocks = [
            {
                "type": "section",
                "text": {
                    "text": "A message *with some bold text* and _some italicized text_.",
                    "type": "mrkdwn",
                },
                "fields": [
                    {"type": "mrkdwn", "text": "High"},
                    {"type": "plain_text", "emoji": True, "text": "String"},
                ],
            }
        ]
        self.test_attachments_in_json = json.dumps(self.test_attachments)
        self.test_blocks_in_json = json.dumps(self.test_blocks)
        self.test_api_params = {'key': 'value'}
        self.expected_method = 'chat.postMessage'
        self.expected_api_params = {
            'channel': self.test_channel,
            'username': self.test_username,
            'text': self.test_text,
            'icon_url': self.test_icon_url,
            'attachments': self.test_attachments_in_json,
            'blocks': self.test_blocks_in_json,
        }
    def __construct_operator(self, test_token, test_slack_conn_id, test_api_params=None):