def genQrelStr(queryId, docId, relGrade):
    """Produces a string representing one QREL entry

    :param queryId:   question/query ID
    :param docId:     relevanet document/answer ID
    :param relGrade:  relevance grade

    :return: a string representing one QREL entry
    """
    return f'{queryId} 0 {docId} {relGrade}'