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() internal {
    owner = msg.sender;
    emit OwnershipTransferred(address(0), owner);
  }

  /**
   * @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 OwnershipTransferred(owner, address(0));
    owner = address(0);
  }
}
function isOwner() public view returns(bool) {
  return msg.sender == owner;
}

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