FILTER_OPERATORS = {
        '_eq',
        '_neq',
        '_lt',
        '_lte',
        '_gt',
        '_gte',
        '_in',
        '_nin',
        '_null',
        '_nnull',
        '_contains',
        '_ncontains',
        '_starts_with',
        '_ends_with',
        '_nends_with',
        '_between',
        '_nbetween',
        '_empty',
        '_nempty',
        '_intersects',
        '_nintersects',
        '_intersects_bbox',
        '_nintersects_bbox',
        }