I have registered the params of two neural nets in a guide with

```
pyro.module("net1", net1)
pyro.module("net2", net2)
```

I’d like to do some `svi.step`

s with the weights in net1 fixed. And then do the same with the weights in net2 fixed. How do I do this?

I tried to do

```
svi_1 = pyro.infer.SVI(model=model,
guide=guide_with_net1on_net2off,
...)
# svi_1 steps...
svi_2 = pyro.infer.SVI(model=model,
guide=guide_with_net1off_net2on,
...)
# svi_2 steps...
```

But the weights in net1 changed by doing `svi_2.step`