[firedrake] Calculate element-wise mass balance

Hello, I am trying to calculate the element-wise mass balance (i.e., \int_{\Omega_element} div(u) d\Omega) over every cell and project the output to DG0 space. Has this been done or is there a way (e.g., with par_loop() ) to implement this in firedrake? This is how I achieved it in fenics: ------------------------------------------------------------------- *cell_domains = CellFunction('size_t', mesh)cell_domains.set_all(0)* *dx = Measure('dx')[cell_domains]area = [cell.volume() for cell in cells(mesh)]* *for i in range(mesh.num_cells()): Error.vector()[i] = (1./area[i]) * assemble(div(solution)*dx(i))* *-------------------------------------------------------------------* Regards, Sarraf