"unpack" a batched expression

[Xiang Yu]

Hi, 

I'm looking for a way to "unpack" a batched expression into list of expressions, like the reverse of the concatenate_to_batch() function. I couldn't find such operation in the doc, is there a simple way to do this without doing a forward pass? Thanks!

[Bhat Irshad]

Any updates on this one, i am looking for something similar.

I have an rnn output batch of the size `((64,), 11)` and i want to pick the last column. I tried `dy.select_cols(fw_exps[0], [last_col_id])` and got `ValueError: Bad arguments in SelectCols: [{64X11}]`.

Is there something like `dy.select_cols_batch`.

[Brian Lester]

```

(_, B) = x.dim()

exps = [dy.pick_batch_elem(x, i) for i in range(B)

```