### Partial derivative and chain rule

I have the following variable and function:

```
var('r')
g = function('g')(r)
```

Now, I define the function `f`

, which depends on `g`

:

```
f = function('f')(g)
```

If I want to compute the derivative `diff(f,r)`

, I get:

```
D[0](f)(g(r))*diff(g(r), r)
```

which is the usual chain rule. However, if I want the derivative with respect to `g`

:

```
diff(f,g)
```

I get an error:

TypeError: argument symb must be a symbol

Is there a way I can calculate the partial derivative of a function? I would expect a symbolic expression, like

$\displaystyle \frac{\partial f}{\partial g}$

I have seen that in REDUCE there is the package DFPART which accounts for derivatives with respect to generic ~~functions.~~functions, but I have not found an analogous module in SageMath.