```\nif (newURl != keccak256(bytes(node.url))) {\n\n    // deleting the old entry\n    delete urlIndex[keccak256(bytes(node.url))];\n\n    // make sure the new url is not already in use\n    require(!urlIndex[newURl].used, "url is already in use");\n\n    UrlInformation memory ui;\n    ui.used = true;\n    ui.signer = msg.sender;\n    urlIndex[newURl] = ui;\n    node.url = \_url;\n}\n```\n