why can't I run probabilistic_matrix_factorization.py

[hl-henry]

Traceback (most recent call last):
File "pmf_demo.py", line 75, in
tf.app.run()
File "/Users/dayi/anaconda3/envs/rs/lib/python3.7/site-packages/tensorflow/python/platform/app.py", line 40, in run
_run(main=main, argv=argv, flags_parser=_parse_flags_tolerate_undef)
File "/Users/dayi/anaconda3/envs/rs/lib/python3.7/site-packages/absl/app.py", line 300, in run
_run_main(main, args)
File "/Users/dayi/anaconda3/envs/rs/lib/python3.7/site-packages/absl/app.py", line 251, in _run_main
sys.exit(main(argv))
File "pmf_demo.py", line 58, in main
inference.run()
File "/Users/dayi/anaconda3/envs/rs/lib/python3.7/site-packages/edward/inferences/inference.py", line 125, in run
self.initialize(*args, **kwargs)
File "/Users/dayi/anaconda3/envs/rs/lib/python3.7/site-packages/edward/inferences/klqp.py", line 110, in initialize
return super(KLqp, self).initialize(*args, **kwargs)
File "/Users/dayi/anaconda3/envs/rs/lib/python3.7/site-packages/edward/inferences/variational_inference.py", line 68, in initialize
self.loss, grads_and_vars = self.build_loss_and_gradients(var_list)
File "/Users/dayi/anaconda3/envs/rs/lib/python3.7/site-packages/edward/inferences/klqp.py", line 145, in build_loss_and_gradients
return build_reparam_kl_loss_and_gradients(self, var_list)
File "/Users/dayi/anaconda3/envs/rs/lib/python3.7/site-packages/edward/inferences/klqp.py", line 717, in build_reparam_kl_loss_and_gradients
qz_copy = copy(qz, scope=scope)
File "/Users/dayi/anaconda3/envs/rs/lib/python3.7/site-packages/edward/util/random_variables.py", line 247, in copy
value, dict_swap, scope, True, copy_q, False)
File "/Users/dayi/anaconda3/envs/rs/lib/python3.7/site-packages/edward/util/random_variables.py", line 89, in _copy_default
x = copy(x, *args, **kwargs)
File "/Users/dayi/anaconda3/envs/rs/lib/python3.7/site-packages/edward/util/random_variables.py", line 271, in copy
new_op = copy(op, dict_swap, scope, True, copy_q, False)
File "/Users/dayi/anaconda3/envs/rs/lib/python3.7/site-packages/edward/util/random_variables.py", line 317, in copy
op_def)
File "/Users/dayi/anaconda3/envs/rs/lib/python3.7/site-packages/tensorflow/python/framework/ops.py", line 2025, in init
op_def, inputs, node_def.attr)
File "/Users/dayi/anaconda3/envs/rs/lib/python3.7/site-packages/tensorflow/python/framework/ops.py", line 2085, in _reconstruct_sequence_inputs
grouped_inputs.append(inputs[i])
IndexError: list index out of range