    def add_args(parser):
        """Add optimizer-specific arguments to the parser."""
        # fmt: off
        parser.add_argument('--lamb-betas', default='(0.9, 0.999)', metavar='B',
                            help='betas for LAMB optimizer')
        parser.add_argument('--lamb-eps', type=float, default=1e-8, metavar='D',
                            help='epsilon for LAMB optimizer')
        parser.add_argument('--weight-decay', '--wd', default=0.0, type=float, metavar='WD',
                            help='weight decay')
Add optimizer-specific arguments to the parser.
fairseq/optim/fused_lamb.py