code: public static byte[][] toByteArray(long[] l) {
          byte[][] b = new byte[l.length][];
          for (int i = 0; i < b.length; i++) {
              b[i] = Bytes.toBytes(l[i]);
          }
          return b;
      }
docs: transforms the given array of longs to an array of byte-arrays
  
  @param l
  the longs to transform
  @return the to l corresponding array of byte-arrays