How to convert a preconditioner matrix into a numpy matrix?

How can I convert a preconditioner matrix c=Preconditioner(a, type="bddc") into a numpy matrix? I didn't find a way to achieve this.

the preconditioners provide a matrix-vector multiplication. It does not make sense to convert them to a dense (numpy) matrix, except for testing.

For tests, you can apply the preconditioner to all unit vectors, and write the result as columns into a dense matrix.

best, Joachim

Thank you. Yes, it's just for testing...