Obviously it is possible to assign any latex text to derivatives by using
the `derivative_func`

option of the `function`

function.

Below I have added an example that I have executed in Sage 6.3.

(Note: edited to make `print`

python3-compatible. Now works in Sage 9.8.)

```
var('z')
def dfx(self, *args, **kwds):
return dfxdz(z)
def dfy(self, *args,**kwds):
return dfydz(z)
fx = function('fx', derivative_func=dfx, latex_name='x')
fy = function('fy', derivative_func=dfy, latex_name='y')
dfxdz = function('dfxdz', latex_name=r'\frac{\operatorname{d}{x}}{\operatorname{d}{z}}')
dfydz = function('dfydz', latex_name=r'\frac{\operatorname{d}{y}}{\operatorname{d}{z}}')
dgdx = function('dgdx', latex_name=r'\frac{\partial{g}}{\partial{x}}')
dgdy = function('dgdy', latex_name=r'\frac{\partial{g}}{\partial{y}}')
pdev = [dgdx(fx(z)), dgdy(fy(z))]
xf = fx(z)
yf = fy(z)
def pderivg(self, *args, **kwds):
print("args:", args)
print("kwds:", kwds, pdev[kwds['diff_param']])
return pdev[int(kwds['diff_param'])]
gf = function('gf', latex_name='g', nargs=2, derivative_func=pderivg)
g = gf(xf, yf)
deriv = g.derivative(z)
show(deriv)
```