How to make a placeholder with changed batches for the dnc state? thanks

I wonder to know how can I create placeholders like dnc_core.initial_state(batch_size=n) with the batch_size n changed in trainning.

> dnc_core = dnc.DNC(...)
> initial_core_state = dnc_core.initial_state(batch_size=1)
> core_state_placeholders = snt.nest.map(lambda t: tf.placeholder(t.dtype, shape=t.shape),
> initial_core_state)

When I create the graph,the shape of initial_state seems be fixed with the batch_size .