@NotNull
  private static Element writeChange(@NotNull Change change) {
    Element changeNode = new Element(NODE_CHANGE);
    writeContentRevision(changeNode, change.getBeforeRevision(), RevisionSide.BEFORE);
    writeContentRevision(changeNode, change.getAfterRevision(), RevisionSide.AFTER);
    return changeNode;
  }
@NotNull
  private static Element writeChange(@NotNull Change change)