Hi!

I try to build the model, in which i exhaust a sequence of some fixed length in the parts of different sizes. But i have problem with enumeration. Here is my code:

## Code

```
def model_8( data ) :
hmmdim = 2
datadim = 3
mwl = 2
x_q = pyro.param( "x_q"
, torch.eye( hmmdim ) * .1 + .1
, constraint=constraints.simplex )
y_q = torch.zeros( [ hmmdim, datadim ** mwl ] )
for i in range( mwl ) :
y_q[i][:datadim ** ( i + 1 )] = .1
y_q = pyro.param( "y_q"
, y_q
, constraint=constraints.simplex )
x = 0
k = torch.tensor( 0 )
for j in pyro.markov( range( len( data ) ) ) :
x = pyro.sample( "x_{}".format( j )
, dist.Categorical( Vindex( x_q )[..., x, :] )
, infer={ "enumerate": "parallel" } )
if k + x + 1 >= len( data ) :
break
obs = torch.tensor( 0, dtype=torch.long )
for i in range( x + 1 ) :
obs += datadim ** i * data[k + i]
pyro.sample( "obs_{}".format(j)
, dist.Categorical( Vindex( y_q )[..., x, :] )
, obs=obs )
k += x + 1
```

I get error: `TypeError: only integer tensors of a single element can be converted to an index`

The general question is: how can i generate observations of different size dependent on enumerated variable?