func: function _transfer(address _from, address _to, uint _value) internal {
  
          require(_to != 0x0);
  
          require(balanceOf[_from] >= _value);
  
          require(balanceOf[_to] + _value > balanceOf[_to]);
  
          require(!frozenAccount[msg.sender]);
  
          require(!frozenAccount[_from]);
  
          require(!frozenAccount[_to]);
  
          
  
          uint previousBalances = balanceOf[_from] + balanceOf[_to];
  
          balanceOf[_from] -= _value;
  
          balanceOf[_to] += _value;
  
          emit Transfer(_from, _to, _value);
  
          assert(balanceOf[_from] + balanceOf[_to] == previousBalances);
  
      }