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 SlackAPIFileOperator(
            task_id='slack',
            token=test_token,
            slack_conn_id=test_slack_conn_id,
            channel=self.test_channel,
            initial_comment=self.test_initial_comment,
            filename=self.test_filename,
            filetype=self.test_filetype,
            content=self.test_content,
            api_params=test_api_params,
        )
    def test_init_with_valid_params(self):
        test_token = 'test_token'
        test_slack_conn_id = 'test_slack_conn_id'
        slack_api_post_operator = self.__construct_operator(test_token, None, self.test_api_params)
        assert slack_api_post_operator.token == test_token
        assert slack_api_post_operator.slack_conn_id is None
        assert slack_api_post_operator.method == self.expected_method
        assert slack_api_post_operator.initial_comment == self.test_initial_comment
        assert slack_api_post_operator.channel == self.test_channel
        assert slack_api_post_operator.api_params == self.test_api_params
        assert slack_api_post_operator.filename == self.test_filename
        assert slack_api_post_operator.filetype == self.test_filetype
        assert slack_api_post_operator.content == self.test_content
        slack_api_post_operator = self.__construct_operator(None, test_slack_conn_id)
        assert slack_api_post_operator.token is None
        assert slack_api_post_operator.slack_conn_id == test_slack_conn_id
    @mock.patch('airflow.providers.slack.operators.slack.SlackHook')
    def test_api_call_params_with_content_args(self, mock_hook):