input: 
  def create_song_class():
      """ Create a class Song with two instance variables, title and artist, and three methods, 
      str(), eq(), and length().
      >>> song1 = Song('Bohemian Rhapsody', 'Queen')
      >>> print(song1)
      Title: Bohemian Rhapsody
      Artist: Queen
      >>> song2 = Song('Bohemian Rhapsody', 'Queen')
      >>> song3 = Song('Another One Bites the Dust', 'Queen')
      >>> song1 == song2
      True
      >>> song1 == song3
      False
      >>> song1.length()
      18
      """
      class Song:
          def __init__(self, title, artist):
              self.title = title
              self.artist = artist
        
          def __str__(self):
              return f'Title: {self.title}\nArtist: {self.artist}'
          
          def __eq__(self, other):
              return self.artist == other.artist and self.title == other.title
  
          def length(self):
              return len(self.title)
      
      return Song
  
output:     class Song:
          def __init__(self, title, artist):
              self.title = title
              self.artist = artist
        
          def __str__(self):
              return f'Title: {self.title}\nArtist: {self.artist}'
          
          def __eq__(self, other):
              return self.artist == other.artist and self.title == other.title
  
          def length(self):
              return len(self.title)
      
      return Song