def METHOD_NAME(operator_with_arrays):
    op, mu, U, V = operator_with_arrays
    op_V = project(op, V, None)
    for dim_range in {None, 0, len(V)//2, len(V)}:
        op_V_sb = project_to_subbasis(op_V, dim_range, None)
        assert op_V_sb.name == op_V.name
        assert op_V_sb.range.dim == (op_V.range.dim if dim_range is None else dim_range)
        assert op_V_sb.source == op_V.source
        range_basis = V if dim_range is None else V[:dim_range]
        op_V_sb2 = project(op, range_basis, None)
        assert np.all(almost_equal(op_V_sb.apply(U, mu=mu),
                                   op_V_sb2.apply(U, mu=mu)))