func: function doSend(
          address _from,
          address _to,
          uint256 _amount,
          bytes _userData,
          address _operator,
          bytes _operatorData,
          bool _preventLocking
      )
          private
      {
          requireMultiple(_amount);
  
          callSender(_operator, _from, _to, _amount, _userData, _operatorData);
  
          require(_to != 0x0);                  
          require(balanceOf[_from] >= _amount); 
  
          balanceOf[_from] = balanceOf[_from].sub(_amount);
          balanceOf[_to] = balanceOf[_to].add(_amount);
  
          callRecipient(_operator, _from, _to, _amount, _userData, _operatorData, _preventLocking);
  
          emit Sent(_operator, _from, _to, _amount, _userData, _operatorData);
          emit Transfer(_from, _to, _amount);
      }