Build a pair of Parallel Transformer encoder/decoder

    Parameters
    ----------
    num_layers : int
    num_heads : int
    scaled : bool
    units : int
    hidden_size : int
    dropout : float
    use_residual : bool
    max_src_length : int
    max_tgt_length : int
    weight_initializer : mx.init.Initializer or None
    bias_initializer : mx.init.Initializer or None
    prefix : str, default 'transformer_'
        Prefix for name of `Block`s.
    params : Parameter or None
        Container for weight sharing between layers.
        Created if `None`.

    Returns
    -------
    encoder : TransformerEncoder
    decoder :TransformerDecoder

def get_transformer_encoder_decoder(num_layers=2,
                                    num_heads=8, scaled=True,
                                    units=512, hidden_size=2048, dropout=0.0, use_residual=True,
                                    max_src_length=50, max_tgt_length=50,
                                    weight_initializer=None, bias_initializer='zeros',
                                    prefix='transformer_', params=None):
    """Build a pair of Parallel Transformer encoder/decoder

    Parameters
    ----------
    num_layers : int
    num_heads : int
    scaled : bool
    units : int
    hidden_size : int
    dropout : float
    use_residual : bool
    max_src_length : int
    max_tgt_length : int
    weight_initializer : mx.init.Initializer or None
    bias_initializer : mx.init.Initializer or None
    prefix : str, default 'transformer_'
        Prefix for name of `Block`s.
    params : Parameter or None
        Container for weight sharing between layers.
        Created if `None`.

    Returns
    -------
    encoder : TransformerEncoder
    decoder :TransformerDecoder
    """
    encoder = TransformerEncoder(num_layers=num_layers,
                                 num_heads=num_heads,
                                 max_length=max_src_length,
                                 units=units,
                                 hidden_size=hidden_size,
                                 dropout=dropout,
                                 scaled=scaled,
                                 use_residual=use_residual,
                                 weight_initializer=weight_initializer,
                                 bias_initializer=bias_initializer,
                                 prefix=prefix + 'enc_', params=params)
    decoder = TransformerDecoder(num_layers=num_layers,
                                 num_heads=num_heads,
                                 max_length=max_tgt_length,
                                 units=units,
                                 hidden_size=hidden_size,
                                 dropout=dropout,
                                 scaled=scaled,
                                 use_residual=use_residual,
                                 weight_initializer=weight_initializer,
                                 bias_initializer=bias_initializer,
                                 prefix=prefix + 'dec_', params=params)
    return encoder, decoder