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contracts...8_Modifiers.sol

pragma solidity 0.8.11;

contract Modifiers {

    address public owner;

    constructor() {
        owner = msg.sender;
    }

    modifier onlyOwner() {
        require(msg.sender == owner, "Not owner");
        _;
    }

    modifier onlyValidAddress(address _newAddress) {
        require(_newAddress != address(0), "Not valid address");
        _;
    }

    function changeOwner(address _newOwner) external onlyOwner onlyValidAddress(_newOwner) {
        owner = _newOwner;
    }
}