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

airflow/providers/slack/operators/slack.py
"""
    Posts messages to a slack channel
    Examples:
    .. code-block:: python
        slack = SlackAPIPostOperator(
            task_id="post_hello",
            dag=dag,
            token="XXX",
            text="hello there!",
            channel="#random",
        )
    :param channel: channel in which to post message on slack name (#general) or
        ID (C12318391). (templated)
    :type channel: str
    :param username: Username that airflow will be posting to Slack as. (templated)
    :type username: str
    :param text: message to send to slack. (templated)
    :type text: str
    :param icon_url: url to icon used for this message
    :type icon_url: str
    :param attachments: extra formatting details. (templated)
        - see https://api.slack.com/docs/attachments.
    :type attachments: list of hashes
    :param blocks: extra block layouts. (templated)
        - see https://api.slack.com/reference/block-kit/blocks.
    :type blocks: list of hashes
    """
    template_fields = ('username', 'text', 'attachments', 'blocks', 'channel')
    ui_color = '#FFBA40'
    def __init__(