defraw_rnn(cell, loop_fn,
parallel_iterations=None, swap_memory=False, scope=None):"""Creates an `RNN` specified by RNNCell `cell` and loop function `loop_fn`.
**NOTE: This method is still in testing, and the API may change.**
This function is a more primitive version of `dynamic_rnn` that provides
more direct access to the inputs each iteration. It also provides more
control over when to start and finish reading the sequence, and
what to emit for the output.
For example, it can be used to implement the dynamic decoder of a seq2seq
model.
Instead of working with `Tensor` objects, most operations work with
`TensorArray` objects directly.
The operation of `raw_rnn`, in pseudo-code, is basically the following:
```python
time = tf.constant(0, dtype=tf.int32)
(finished, next_input, initial_state, emit_structure, loop_state) = loop_fn(
time=time, cell_output=None, cell_state=None, loop_state=None)
emit_ta = TensorArray(dynamic_size=True, dtype=initial_state.dtype)
state = initial_state
while not all(finished):
(output, cell_state) = cell(next_input, state)
(next_finish