input: Write a python function to check if the server is running and returns 'Hello World!' for a GET request.
  assert check_server('http://localhost:8080') == True
  assert check_server('http://localhost:8081') == False
  assert check_server('http://localhost:8080/notfound') == False
output: def check_server(url):
      import requests
      try:
          response = requests.get(url)
          if response.status_code == 200 and response.text == 'Hello World!':
              return True
          else:
              return False
      except requests.exceptions.RequestException:
          return False