I have a little model here which has vectorized plate and markov context, and it gives strange error.

*‘Tensor’ object has no attribute ‘_pyro_backward’*

The strange thing is that if you delete any one of the **a** and **b** variable, the error disappear, which means that they worked well on their own and conflicted when working together, however, this two variables are set to be independent.

This model has no practical meanings, but it seems that this model doesn’t break any rules, so i guess that this model revealed some bugs.

I searched in the forum and found no relevant information, please help me! Thanks!

```
import torch
import pyro
import pyro.distributions as dist
from pyro.infer import TraceEnum_ELBO, config_enumerate
@config_enumerate
def model():
with pyro.plate('plate', size=2, dim=-1):
a = pyro.sample('a', dist.Dirichlet(concentration=torch.ones(2)))
for T in pyro.markov(range(2)):
b = pyro.sample('b{}'.format(T), dist.Categorical(
probs=torch.ones(2)), infer={'enumerate': None})
@config_enumerate(default='sequential')
def guide():
with pyro.plate('plate', size=2, dim=-1):
a_param=pyro.param('a_param',torch.ones(2))
a = pyro.sample('a', dist.Dirichlet(concentration=a_param))
for T in pyro.markov(range(2)):
b_param=pyro.param('b_param',torch.ones(2))
b = pyro.sample('b{}'.format(T), dist.Categorical(probs=b_param))
pyro.clear_param_store()
elbo = TraceEnum_ELBO()
print(elbo.loss(model, guide))
```

The error is as follows

**AttributeError** Traceback (most recent call last) **e:\Project\sim\sim_2p_2l.py** in 27 pyro **.** clear_param_store **(** **)** 28 elbo **=** TraceEnum_ELBO **(** **)** **—> 29** print **(** elbo **.** loss **(** generative_model **,** guide **)** **)** **c:\Users\yaowang.conda\envs\my_env\lib\site-packages\pyro\infer\traceenum_elbo.py** in loss **(self, model, guide, *args, **kwargs)** 403 elbo **=** **0.0** 404 **for** model_trace **,** guide_trace **in** self **.** _get_traces **(** model **,** guide **,** args **,** kwargs **)** **:** ** → 405** elbo_particle **=** _compute_dice_elbo **(** model_trace **,** guide_trace **)** 406 **if** is_identically_zero **(** elbo_particle **)** **:** 407 **continue** **c:\Users\yaowang.conda\envs\my_env\lib\site-packages\pyro\infer\traceenum_elbo.py** in _compute_dice_elbo **(model_trace, guide_trace)** 212 costs **.** setdefault **(** ordering **[** name **]** **,** **[** **]** **)** **.** append **(** cost **)** 213 ** → 214 return** Dice

**(**guide_trace

**,**ordering

**)**

**.**compute_expectation

**(**costs

**)**215 216

**c:\Users\yaowang.conda\envs\my_env\lib\site-packages\pyro\infer\util.py**in compute_expectation

**(self, costs)**296 require_backward

**(**query

**)**297 root

**=**ring

**.**sumproduct

**(**log_factors

**,**sum_dims

**)**

**→ 298**root

**.**_pyro_backward

**(**

**)**299 probs = { 300 key

**:**query

**.**_pyro_backward_result

**.**exp

**(**

**)**

**AttributeError**: ‘Tensor’ object has no attribute ‘_pyro_backward’