contract Ownable {
  address public owner;

  function Ownable() public {
    owner = msg.sender;
  }

  modifier onlyOwner() {
    require(msg.sender == owner);
    _;
  }
  //transfer owner to another address
  function transferOwnership(address _newOwner) public onlyOwner {
    if (_newOwner != address(0)) {
      owner = _newOwner;
    }
  }
}
function transferOwnership(address _newOwner) public onlyOwner {
  if (_newOwner != address(0)) {
    owner = _newOwner;
  }
}

//transfer owner to another address