def METHOD_NAME():
    """Solve a simple problem with a custom linear solver."""
    problem = RadiationProblem(body=sphere, omega=1.0, water_depth=np.infty)
    reference_solver = BEMSolver(
        engine=BasicMatrixEngine(linear_solver="gmres", matrix_cache_size=0)
    )
    reference_result = reference_solver.solve(problem)
    def my_linear_solver(A, b):
        """A dumb solver for testing."""
        return np.linalg.inv(A) @ b
    my_bem_solver = BEMSolver(
        engine=BasicMatrixEngine(linear_solver=my_linear_solver, matrix_cache_size=0)
    )
    assert 'my_linear_solver' in my_bem_solver.exportable_settings['linear_solver']
    result = my_bem_solver.solve(problem)
    assert np.isclose(reference_result.added_masses['Surge'], result.added_masses['Surge'])