Small typo in tutorial notebook on Normalizing Flows

[felixschltr]

Hi,

there seems to be a small typo in the tutorial notebook on normalizing flows in section "Fixed Univariate Transforms in Pyro".

The log-absolute derivative of the exponential transform $y = g(x) = \exp(x)$ is stated as $\log(\vert\frac{dg}{dx}\vert)=y$ while it should rather be $\log(\vert\frac{dg}{dx}\vert)=x$ (see also the implementation of torch.distributions.transforms.ExpTransform).

[fritzo]

Yes, I think you're right:

g(x) = exp(x)
dg/dx = d/dx exp(x)
      = exp(x)
      > 0
|dg/dx| = dg/dx
        = exp(x)
log(|dg/dx|) = x

Typo fix is welcome 😄 !