code: public Maybe<DbxEntry./*@Nullable*/WithChildren> getMetadataWithChildrenIfChanged(String path, boolean includeMediaInfo, /*@Nullable*/String previousFolderHash)
          throws DbxException
      {
          return getMetadataWithChildrenIfChangedBase(path, includeMediaInfo, previousFolderHash, DbxEntry.WithChildren.ReaderMaybeDeleted);
      }
docs: Get the metadata for a given path and its children if anything has
  changed since the last time you got them (as determined by the value
  of {@link DbxEntry.WithChildren#hash} from the last result).
  
  @param path
  The path (starting with "/") to the file or folder (see {@link DbxPathV1}).
  
  @param previousFolderHash
  The value of {@link DbxEntry.WithChildren#hash} from the last time
  you got the metadata for this folder (and children).
  
  @return Never returns {@code null}.  If the folder at the given path hasn't changed
  since you last retrieved it (i.e. its contents match {@code previousFolderHash}), return
  {@code Maybe.Nothing}.  If it doesn't match {@code previousFolderHash} return either
  {@code Maybe.Just(null)} if there's nothing there or {@code Maybe.Just} with the
  metadata.