Hello,

I want to pass a relationship based on the solution of the problem to a python function as a float in every time step. Here a sample of my solution loop:

```
while (time <= T):
# solve the system and obtain the solution (u,trz)
nIter, rNorm = NewtonRaphson(Res,Jac,bcs_,uknown,uknown0,rank)
# split the unkown
u,trz = uknown.split(True)
# Define a tensor based on the solution of the u
F = as_tensor([[u,0.,0.],[0.,u,0.],[0.,0.,1.]])
# Define a scalar quantity
FF = inner(F,F)
# pass this scalar to a python function and take the output "out" which is a float
out = reaction(FF)
# Move to next time step
u0.assign(u)
trz0.assign(trz)
time += dt
```

I want to pass the quantity FF, as a float, to a python function reaction() to solve a system of ODEs with solve_ivp of scipy. How can I do it ?

Thanks you