Function update dependent on time in mixed Element

General
1 
Version: Dolfinx 0.6.0 Python
Windows Subsystem for Linux (WSL) in Visual Studio Code

Hello guys,  I’ve been trying to solve an Termo-elasticity coupling problem, and I’ve been faced with some problems.
As I want to observe the transient region of the problem, I need to perform a discretization in time, a behavior similar to the Thermo-elastic evolution problem (full coupling):
https://comet-fenics.readthedocs.io/en/latest/demo/thermoelasticity/thermoelasticity_transient.html

Some questions are:
1. How to determine an initial condition, t=0. For a mixed element:

from dolfinx import*

"""Function Space"""
Vue = VectorElement('Lagrange', domain.ufl_cell(), 1) # displacement finite element
Vte = FiniteElement('Lagrange', domain.ufl_cell(), 1) # temperature finite element
V = fem.FunctionSpace(domain, MixedElement([Vue, Vte]))

U_ = TestFunction(V)
(u_, Theta_) = split(U_)


W = TrialFunction(V)
(du, dTheta) = split(W)

2. How to obtain Solution components from mixed elements, and update them for the next time step.
I saw some implementation models to have some reference, such as through interpolation: https://fenicsproject.discourse.group/t/issue-with-updating-time-in-mixed-space/6086/6, 
however, I m not managing to interpolate the components of the mixed space for updating over time.

for (i, dti) in enumerate(np.diff(t)):
    print("Increment " + str(i+1))
    dt +=(dti)
    uh = problem.solve()
    Uold.sub(1).interpolate(uh.sub(1))
    xdmf.write_function(Uold.sub(1),dt)

Finally, I apologize for my ignorance, any help will be welcome.
2

See Initial Conditions for mixed Element - #10 by dokken

Similarly, use a FunctionAssigner

3

Sorry, I didn’t clarify that it is for the updated version of Dolfinx. I will update the post.

4

See for instance: How to correctly assign values to mixed elements in FEniCS-X? - #3 by dokken
Using the map from a collapsed sub function to the parent space, you can assign to a subset of your vector.

Please also split your post in to pure text, and code boxes, such as

```python
import dolfinx
# Add more code here
```