So I copied and modified that start of schwarzschild.cnb to my own notebook which I'll call Laplacian.cnb

I modified the first code block to add some more coordinates vr, vtheta, vphi (intended to represent velocities -- I'm working in velocity phase space).

```
{t,r,\theta,\phi, vt, vr, vtheta, vphi}::Coordinate;
{\mu,\nu,\rho,\sigma,\lambda,\kappa,\chi,\gamma}::Indices(values={t,r,\phi,\theta}, position=fixed);
\partial{#}::PartialDerivative;
g_{\mu\nu}::Metric.
g^{\mu\nu}::InverseMetric.
```

Now I try to define a simple (scalar) function
f, which is just `f() = r + vtheta**2`

and try to evaluate `\partial_r f`

. My code block is

```
f::Depends(r,\theta,\phi, vr, vtheta, vphi);
exf:= { f = r + vtheta**2 } ;
exfr:= { fr = \partial_r{f} };
evaluate(exfr,exf);
```

The final line of output is just `\partial_r f`

.
I.e., it didn't perform the partial derivative.
(The answer should have been 1.)

What am I doing wrong?