def _structure_parent_category(_parent_id, _payload):
    """This function structures the portion of the payload for the parent category.

    .. versionadded:: 2.5.0

    :param _parent_id: The ID of the parent category (if applicable)
    :type _parent_id: str, None
    :param _payload: The partially constructed payload for the API request
    :type _payload: dict
    :returns: The API request payload with appended entries for ``parent_category``
    """
    if _parent_id:
        _payload['data']['parent_category'] = {
            'id': _parent_id
        }
    return _payload