@classmethod
def __get_query_range(cls, date_field, start=None, end=None):
    """
        Create a filter dict with date_field from start to end dates.

        :param date_field: field with the date value
        :param start: date with the from value. Should be a datetime.datetime object
                      of the form: datetime.datetime(2018, 5, 25, 15, 17, 39)
        :param end: date with the to value. Should be a datetime.datetime object
                      of the form: datetime.datetime(2018, 5, 25, 15, 17, 39)
        :return: a dict containing a range filter which can be used later in an
                 es_dsl Search object using the `filter` method.
        """
    if not start and not end:
        return ''
    start_end = {}
    if start:
        start_end['gte'] = '%s' % start.isoformat()
    if end:
        start_end['lte'] = '%s' % end.isoformat()
    query_range = {date_field: start_end}
    return query_range
