contract Ownable {
    address public owner;
    event OwnershipTransferred(
        address indexed previousOwner,
        address indexed newOwner
    );

    /**
     * @dev The Ownable constructor sets the original `owner` of the contract to the sender account.
     **/
    constructor() public {
        owner = msg.sender;
    }

    /**
     * @dev Throws if called by any account other than the owner.
     **/
    modifier onlyOwner() {
        require(msg.sender == owner, "only owner can make this transaction");
        _;
    }

    /**
     * @dev Allows the current owner to transfer control of the contract to a newOwner.
     * @param newOwner The address to transfer ownership to.
     **/
    function transferOwnership(address newOwner) public onlyOwner {
        require(
            newOwner != address(0),
            "new owner can not be a zero address"
        );
        emit OwnershipTransferred(owner, newOwner);
        owner = newOwner;
    }
}
/**
 * @title Ownable
 * @dev The Ownable contract has an owner address, and provides basic authorization control
 * functions, this simplifies the implementation of "user permissions".
 **/
function transferOwnership(address newOwner) public onlyOwner {
        require(
            newOwner != address(0),
            "new owner can not be a zero address"
        );
        emit OwnershipTransferred(owner, newOwner);
        owner = newOwner;
    }
/**
 * @dev Allows the current owner to transfer control of the contract to a newOwner.
 * @param newOwner The address to transfer ownership to.
 **/