Use of PWMatrixCoefficient to define matrix coefficients per attribute

[mdavids-cfs]

Hi all,
I have been trying to implement a PWMatrixCoefficient but I am having trouble with the interface (also couldn't find an example for this). The goal is to assign a MatrixConstantCoefficient per mesh attribute.
In normal MFEM (C++) this is done by creating an Array Array<MatrixCoefficient *> coefs(0); and then assigning the matrix coefficients. I thought that PyMFEM can interpret normal lists of tuples as list-equivalents, i.e., I tried something like this:

sigma_all_coefs = []
sigma_attr = mfem.intArray(max_attr)
for ti,tensor in enumerate(sigma_all): 
    # just for testing
    temp = mfem.DenseMatrix(dim)
    temp.Assign(0.0)

    # add matrix coefficient to list
    sigma_all_coefs.append(mfem.MatrixConstantCoefficient(temp)  )
    sigma_attr[ti] = ti+1   
    
# Create PW Matrix Coefficient
sigmaCoef = mfem.PWMatrixCoefficient(dim, sigma_attr, sigma_all_coefs, False)

which fails when calling the mfem.PWMatrixCoefficient constructor. Also tried another approach:

# Create PW Matrix Coefficient
sigmaCoef = mfem.PWMatrixCoefficient(dim, False)

for ti, tensor in enumerate(sigma_all):
    # Set coefficient
    sigmaCoef.UpdateCoefficient( ti+1, mfem.MatrixConstantCoefficient( mfem.DenseMatrix(tensor) ) )

which fails when attempting to assemble a bilinear operator, that utilizes the PWMatrixCoefficient.

Any thoughts on how this could be achieved?
Big thanks and warm regards,
Mathias