public MemorySize divide(long by) {
        if (by < 0) {
            throw new IllegalArgumentException("divisor must be != 0");
        }
        return new MemorySize(bytes / by);
    }
@Test
    void testDivideByLong() {
        final MemorySize memory = new MemorySize(100L);
        assertThat(memory.divide(23)).isEqualTo(new MemorySize(4L));
    }