def _ensure_timestamp_field(dataset_expr, deltas):
    measure = dataset_expr.dshape.measure
    if TS_FIELD_NAME not in measure.names:
        dataset_expr = bz.transform(
            dataset_expr,
            **{TS_FIELD_NAME: dataset_expr[AD_FIELD_NAME]}
        )
        if deltas is not None:
            deltas = bz.transform(
                deltas,
                **{TS_FIELD_NAME: deltas[AD_FIELD_NAME]}
            )
    else:
        _check_datetime_field(TS_FIELD_NAME, measure)

    return dataset_expr, deltas
fieldname is the field to search.
dataset/ETHPy150Open quantopian/zipline/zipline/pipeline/loaders/blaze/core.py/_ensure_timestamp_field--crossover with--dataset/ETHPy150Open tallstreet/Whoosh-AppEngine/src/whoosh/query.py/Phrase.__init__