public void login(IWebDriver driver, string user_name, string password)
{
var wait_login = new WebDriverWait(driver, TimeSpan.FromSeconds(20));
driver.Navigate().GoToUrl(login_url);
IWebElement user = wait_login.Until(username => username.FindElement(By.Id("loginForm:email")));
IWebElement pass = wait_login.Until(Pass => Pass.FindElement(By.Id("loginForm:inputPassword")));
clear_fields(user, pass);
user.SendKeys(user_name);
pass.SendKeys(password);
Thread.Sleep(1500);
wait_login.Until(sign_in => sign_in.FindElement(By.Id("loginForm:loginBtn"))).Click();
}