code: public byte[] getMacFragment() {
          if (getVersion() != 'b')
              return null;
  
          byte[] x = new byte[6];
  
          x[0] = 0;
          x[1] = 0;
          x[2] = (byte) (content[6] & 0xF);
          x[3] = content[7];
          x[4] = content[8];
          x[5] = content[9];
  
          return x;
      }
docs: Extract MAC address fragment from raw UUID bytes, setting missing values to 0, thus the first 2 and a half bytes
  will be 0, followed by 3 and a half bytes of the active MAC address when the UUID was generated.
  @return Byte array of UUID fragment, or null for unrecognized format.