input: Write a python function to get the rating of a movie using IMDbPY library.
  assert get_movie_rating('The Prestige') == 8.5
  assert get_movie_rating('Inception') == 8.8
  assert get_movie_rating('The Godfather') == 9.2
output: def get_movie_rating(title):
      from imdb import IMDb
  
      ia = IMDb()
      movies = ia.search_movie(title)
  
      if not movies:
          return None
  
      movie = ia.get_movie(movies[0].movieID)
      return movie.get('rating')