@Override
  public String toString() {
    return '{' + Hex.u2(label) + '}';
  }
Returns an instance that is identical to this one, except that the registers in each
instruction are offset by the given amount.

@param delta the amount to offset register numbers by
@return {@code non-null;} an appropriately-constructed instance
android/android_framework/dex-maker/src/main/java/com/android/dx/rop/code/BasicBlock.java