contract Ownable {

  address private _owner;
  uint256 private _ownershipLocked;

  event OwnershipLocked(address lockedOwner);
  event OwnershipRenounced(address indexed previousOwner);
  event OwnershipTransferred(
    address indexed previousOwner,
    address indexed newOwner
  );


  constructor() public {
    _owner = msg.sender;
  _ownershipLocked = 0;
  }

  function owner() public view returns(address) {
    return _owner;
  }

  modifier onlyOwner() {
    require(isOwner());
    _;
  }

  function isOwner() public view returns(bool) {
    return msg.sender == _owner;
  }

  function transferOwnership(address newOwner) public onlyOwner {
    _transferOwnership(newOwner);
  }

  function _transferOwnership(address newOwner) internal {
    require(_ownershipLocked == 0);
    require(newOwner != address(0));
    emit OwnershipTransferred(_owner, newOwner);
    _owner = newOwner;
  }
  
  // Set _ownershipLocked flag to lock contract owner forever
  function lockOwnership() public onlyOwner {
  require(_ownershipLocked == 0);
  emit OwnershipLocked(_owner);
    _ownershipLocked = 1;
  }

}
function lockOwnership() public onlyOwner {
require(_ownershipLocked == 0);
emit OwnershipLocked(_owner);
  _ownershipLocked = 1;
}

// Set _ownershipLocked flag to lock contract owner forever