func: function doBurn(address _operator, address _tokenHolder, uint256 _amount, bytes _holderData, bytes _operatorData)
      internal
    {
      requireMultiple(_amount);
      require(balanceOf(_tokenHolder) >= _amount);
  
      mBalances[_tokenHolder] = mBalances[_tokenHolder].sub(_amount);
      mTotalSupply = mTotalSupply.sub(_amount);
  
      callSender(_operator, _tokenHolder, 0x0, _amount, _holderData, _operatorData);
      emit Burned(_operator, _tokenHolder, _amount, _holderData, _operatorData);
    }