input: Write a python function to fill out a form using Selenium.
  ```python
  from selenium import webdriver
  
  def fill_form(browser, url, name, email, age):
      browser.get(url)
      browser.find_element_by_id("name").send_keys(name)
      browser.find_element_by_id("email").send_keys(email)
      browser.find_element_by_id("age").send_keys(age)
      browser.find_element_by_id("submit").click()
  
  # Test cases
  browser = webdriver.Chrome()
  fill_form(browser, "website_url", "John Doe", "example@domain.com", "25")
  assert browser.find_element_by_id("name").get_attribute("value") == "John Doe"
  assert browser.find_element_by_id("email").get_attribute("value") == "example@domain.com"
  assert browser.find_element_by_id("age").get_attribute("value") == "25"
output: from selenium.webdriver.common.by import By
  
  def fill_form(browser, url, name, email, age):
      browser.get(url)
      browser.find_element(By.ID, "name").send_keys(name)
      browser.find_element(By.ID, "email").send_keys(email)
      browser.find_element(By.ID, "age").send_keys(age)
      browser.find_element(By.ID, "submit").click()
  
  # Test cases
  browser = webdriver.Chrome()
  fill_form(browser, "website_url", "John Doe", "example@domain.com", "25")
  assert browser.find_element(By.ID, "name").get_attribute("value") == "John Doe"
  assert browser.find_element(By.ID, "email").get_attribute("value") == "example@domain.com"
  assert browser.find_element(By.ID, "age").get_attribute("value") == "25"