contract Ownable {
address private _owner;


event OwnershipRenounced(address indexed previousOwner);
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;
}

/**
  * @return the address of the owner.
  */
function owner() public view returns(address) {
  return _owner;
}

/**
  * @dev Throws if called by any account other than the owner.
  */
modifier onlyOwner() {
  require(isOwner());
  _;
}

/**
  * @return true if `msg.sender` is the owner of the contract.
  */
function isOwner() public view returns(bool) {
  return msg.sender == _owner;
}

/**
  * @dev Allows the current owner to relinquish control of the contract.
  * @notice Renouncing to ownership will leave the contract without an owner.
  * It will not be possible to call the functions with the `onlyOwner`
  * modifier anymore.
  */
function renounceOwnership() public onlyOwner {
  emit OwnershipRenounced(_owner);
  _owner = address(0);
}

/**
  * @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 {
  _transferOwnership(newOwner);
}

/**
  * @dev Transfers control of the contract to a newOwner.
  * @param newOwner The address to transfer ownership to.
  */
function _transferOwnership(address newOwner) internal {
  require(newOwner != address(0));
  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 isOwner() public view returns(bool) {
  return msg.sender == _owner;
}

/**
 * @return true if `msg.sender` is the owner of the contract.
 */