def opt_to_kwargs(opt):
    """Get kwargs for seq2seq from opt."""
    kwargs = {}
    for k in ['numlayers', 'dropout', 'bidirectional', 'rnn_class',
        'lookuptable', 'decoder', 'numsoftmax', 'attention',
        'attention_length', 'attention_time', 'input_dropout']:
        if k in opt:
            kwargs[k] = opt[k]
    return kwargs
