Tau/Delta composition derivatives not available for multifluid_mutant

[fefiedler]

Hi Ian,

I created a multifluid_mutant in python from a teqp basemodel. The basemodel has the composition derivative functions of tau and delta, like get_AtaudeltaXi, attached but the mutant not.
Here is the error when I call:

mutant.get_AtaudeltaXi(tau,ntau,delta,ndelta,x,comp,nx)

RuntimeError: Cannot take derivatives of a class that doesn't define the alphar_taudelta method

The derivative at constant temperature/density is working:

mutant.get_ATrhoXi(Temp, nt, rho, nrho, x, comp, nx)

[ianhbell]

Thanks for the bug report. Fix is done and being tested