updated the evaluation script for retriver

    # parameters for Av.rank validation method

    # Following options/arguments have been taken directly from DPR codebase

    #group.add_argument("--val-av-rank-start-epoch", type=int, default=10000,

    #                    help="Av.rank validation: the epoch from which to enable this validation")

    group.add_argument('--val-av-rank-hard-neg', type=int, default=30,

                        help='Av.rank validation: how many hard negatives to'

                        ' take from each question pool')

    group.add_argument('--val-av-rank-other-neg', type=int, default=30,

                        help='Av.rank validation: how many other negatives to'

                        ' take from each question pool')

    #group.add_argument("--val-av-rank-bsz", type=int, default=128,

    #                    help="Av.rank validation: batch size to process passages")

    #group.add_argument("--val-av-rank-max-qs", type=int, default=10000,

    #                    help="Av.rank validation: max num of questions")

    return parser