input: Write a python function to mimic the behavior of the Movie Resource class using a dictionary to store movie information.
  assert movie_resource("post", "Inception", year="2010", rating="8.8") == {'year': '2010', 'rating': '8.8'}
  assert movie_resource("get", "Inception") == {'year': '2010', 'rating': '8.8'}
  assert movie_resource("put", "Inception", year="2011", rating="9.0") == {'year': '2011', 'rating': '9.0'}
  assert movie_resource("delete", "Inception") == ''
  assert movie_resource("get", "Inception") == None
output: def movie_resource(action, title, **kwargs):
      movie_db = {}
  
      if action == "post":
          movie_db[title] = kwargs
          return movie_db[title]
      elif action == "get":
          return movie_db.get(title)
      elif action == "put":
          if title in movie_db:
              movie_db[title].update(kwargs)
              return movie_db[title]
      elif action == "delete":
          return movie_db.pop(title, '')
  ```
  
  ```python
  # Persistence across function calls is required. Use a global dictionary to store the movie information.
  movie_db = {}
  
  def movie_resource(action, title, **kwargs):
      global movie_db
  
      if action == "post":
          movie_db[title] = kwargs
          return movie_db[title]
      elif action == "get":
          return movie_db.get(title)
      elif action == "put":
          if title in movie_db:
              movie_db[title].update(kwargs)
              return movie_db[title]
      elif action == "delete":
          return movie_db.pop(title, '')