problem in running simple LSTM

[srinathdwivedi]

the error occurred is:
Traceback (most recent call last):
File "/home/srinath/char_gen.py", line 63, in
model.add(LSTM(256, input_shape=(x.shape[2], x.shape[1]), return_sequences=True))
File "/home/srinath/anaconda3/lib/python3.6/site-packages/keras/engine/sequential.py", line 166, in add
layer(x)
File "/home/srinath/anaconda3/lib/python3.6/site-packages/keras/layers/recurrent.py", line 500, in call
return super(RNN, self).call(inputs, **kwargs)
File "/home/srinath/anaconda3/lib/python3.6/site-packages/keras/engine/base_layer.py", line 460, in call
output = self.call(inputs, **kwargs)
File "/home/srinath/anaconda3/lib/python3.6/site-packages/keras/layers/recurrent.py", line 2112, in call
initial_state=initial_state)
File "/home/srinath/anaconda3/lib/python3.6/site-packages/keras/layers/recurrent.py", line 609, in call
input_length=timesteps)
File "/home/srinath/anaconda3/lib/python3.6/site-packages/keras/backend/tensorflow_backend.py", line 2957, in rnn
maximum_iterations=input_length)
TypeError: while_loop() got an unexpected keyword argument 'maximum_iterations'
ERROR:tensorflow:==================================
Object was never used (type <class 'tensorflow.python.ops.tensor_array_ops.TensorArray'>):
<tensorflow.python.ops.tensor_array_ops.TensorArray object at 0x7f7901757dd8>
If you want to mark it as used call its "mark_used()" method.
It was originally created here:
['File "/home/srinath/char_gen.py", line 63, in \n model.add(LSTM(256, input_shape=(x.shape[2], x.shape[1]), return_sequences=True))', 'File "/home/srinath/anaconda3/lib/python3.6/site-packages/keras/engine/sequential.py", line 166, in add\n layer(x)', 'File "/home/srinath/anaconda3/lib/python3.6/site-packages/keras/layers/recurrent.py", line 500, in call\n return super(RNN, self).call(inputs, **kwargs)', 'File "/home/srinath/anaconda3/lib/python3.6/site-packages/keras/engine/base_layer.py", line 460, in call\n output = self.call(inputs, **kwargs)', 'File "/home/srinath/anaconda3/lib/python3.6/site-packages/keras/layers/recurrent.py", line 2112, in call\n initial_state=initial_state)', 'File "/home/srinath/anaconda3/lib/python3.6/site-packages/keras/layers/recurrent.py", line 609, in call\n input_length=timesteps)', 'File "/home/srinath/anaconda3/lib/python3.6/site-packages/keras/backend/tensorflow_backend.py", line 2877, in rnn\n input_ta = input_ta.unstack(inputs)', 'File "/home/srinath/anaconda3/lib/python3.6/site-packages/tensorflow/python/util/tf_should_use.py", line 170, in wrapped\n return _add_should_use_warning(fn(*args, **kwargs))', 'File "/home/srinath/anaconda3/lib/python3.6/site-packages/tensorflow/python/ops/tensor_array_ops.py", line 413, in unstack\n indices=math_ops.range(0, num_elements), value=value, name=name)', 'File "/home/srinath/anaconda3/lib/python3.6/site-packages/tensorflow/python/util/tf_should_use.py", line 170, in wrapped\n return _add_should_use_warning(fn(*args, **kwargs))', 'File "/home/srinath/anaconda3/lib/python3.6/site-packages/tensorflow/python/util/tf_should_use.py", line 139, in _add_should_use_warning\n wrapped = TFShouldUseWarningWrapper(x)', 'File "/home/srinath/anaconda3/lib/python3.6/site-packages/tensorflow/python/util/tf_should_use.py", line 96, in init\n stack = [s.strip() for s in traceback.format_stack()]']