@CanIgnoreReturnValue
  public Replacements add(Replacement replacement) {
    return add(replacement, CoalescePolicy.REJECT);
  }
@Test
  public void identicalDuplicatesOK() {
    Replacements replacements = new Replacements();
    replacements.add(Replacement.create(42, 43, "hello"));
    replacements.add(Replacement.create(42, 43, "hello"));
  }