def get_next_id(self):
        try:
            query = {'_id': 'last_id'}
            update = {'$inc': {'id': 1}}
            fn = self.db.internal.find_and_modify
            row = fn(query, update, upsert=True, new=True)
        except Exception as e:
            raise DatabaseException(e)
        return row['id']
def test_ccode_user_functions():
    x = symbols('x', integer=False)
    n = symbols('n', integer=True)
    custom_functions = {
        "ceiling": "ceil",
        "Abs": [(lambda x: not x.is_integer, "fabs"), (lambda x: x.is_integer, "abs")],
    }
    assert ccode(ceiling(x), user_functions=custom_functions) == "ceil(x)"
    assert ccode(Abs(x), user_functions=custom_functions) == "fabs(x)"
    assert ccode(Abs(n), user_functions=custom_functions) == "abs(n)"