recurrent_group cannot return more than one layer as its outputs.

[lcy-seso]

I use machine translation in PaddleBook as the test example.

• Previously, recurrent_group in PaddlePaddle can return more than one layers inside the layer group as its outputs.
• The returned layers are accessible to any other layers in the network, while layers inside recurrent_group (and is not returned by recurrent_gropu) are not accessible outside the recurrent_group.
• I hope to use the above feature, but if I change this line to return more than one layers in recurrent_group, the configuration parsing process crashes. It seems that there is some bug?
• the error information is as follows:

Traceback (most recent call last):
  File "network_conf.py", line 114, in <module>
    print parse_network(seq_to_seq_net(30000, 30000, True, 3, 250))
  File "network_conf.py", line 108, in seq_to_seq_net
    max_length=max_length)
  File "/home/caoying/paddle_codes/models/nmt_plot_attention_weights/paddle/v2/config_base.py", line 52, in wrapped
    out = f(*args, **xargs)
  File "/home/caoying/paddle_codes/models/nmt_plot_attention_weights/paddle/trainer_config_helpers/default_decorators.py", line 53, in __wrapper__
    return func(*args, **kwargs)
  File "/home/caoying/paddle_codes/models/nmt_plot_attention_weights/paddle/trainer_config_helpers/layers.py", line 3949, in beam_search
    is_generating=True)
  File "/home/caoying/paddle_codes/models/nmt_plot_attention_weights/paddle/trainer_config_helpers/default_decorators.py", line 53, in __wrapper__
    return func(*args, **kwargs)
  File "/home/caoying/paddle_codes/models/nmt_plot_attention_weights/paddle/trainer_config_helpers/layers.py", line 3657, in recurrent_group
    RecurrentLayerGroupEnd(name=name)
  File "/home/caoying/paddle_codes/models/nmt_plot_attention_weights/paddle/trainer/config_parser.py", line 396, in RecurrentLayerGroupEnd
    "memory declare wrong size:%d" % memory_link.size)
  File "/home/caoying/paddle_codes/models/nmt_plot_attention_weights/paddle/trainer/config_parser.py", line 156, in config_assert
    logger.fatal(msg)
  File "/home/caoying/paddle_codes/models/nmt_plot_attention_weights/paddle/trainer/config_parser.py", line 3531, in my_fatal
    raise Exception()
Exception