@Override
  public String toString() {
    return ioStatisticsToString(this);
  }
@Test
  public void testStringification2() throws Throwable {

    String ss = snapshot.toString();
    LOG.info("original {}", ss);
    Assertions.assertThat(ss)
        .describedAs("snapshot toString()")
        .contains("c1=0")
        .contains("g1=1");
  }