I am new to Pyro and trying to implement the classification task of MNIST dataset using Bayesian Neural Network. In `Model`

, I have such a line:

```
pyro.sample("obs", Categorical(logits=lhat), obs=y_data)
```

Based on my understanding, this function samples from a conditional distribution given an observation, which is just the inference algorithm.

My question is: why `obs`

in this case is the `y_data`

, not `x_data`

? My understanding is that we make the inference given the observation which is `x_data`

.

Any intuitive explanation is appreciated!