code: public static Guid fromHasGuid(HasGuid... objs) throws IOException {
      byte[][] byteArrays = new byte[objs.length][];
      for (int i = 0; i < objs.length; i++) {
        byteArrays[i] = objs[i].guid().sha;
      }
      return fromByteArrays(byteArrays);
    }
docs: Generate a {@link Guid} for an array of {@link HasGuid}.
  @param objs array of {@link HasGuid}.
  @return a single {@link Guid} for the array.
  @throws IOException