@Override
  public void returnOperation(AbstractInsnNode insn, DataValue value, DataValue expected) {
    if (insn.getOpcode() == Opcodes.ARETURN) {
      if (returnValue == null) {
        returnValue = value;
      }
      else if (!returnValue.equals(value)) {
        returnValue = DataValue.UnknownDataValue1;
      }
    }
  }
@Override
  public void returnOperation(AbstractInsnNode insn, DataValue value, DataValue expected)