input: Write a function to create a Python class named Song with two instance variables, title and artist, and three methods, str(), eq(), and length(). The str() method should return a formatted string displaying the song's title and artist, the eq() method should compare two Song objects for equality based on their title and artist, and the length() method should return the length of the song's title.
  
  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)
  
  assert str(Song('Bohemian Rhapsody', 'Queen')) == 'Title: Bohemian Rhapsody\nArtist: Queen'
  assert str(Song('Stairway to Heaven', 'Led Zeppelin')) == 'Title: Stairway to Heaven\nArtist: Led Zeppelin'
  assert Song('Bohemian Rhapsody', 'Queen') == Song('Bohemian Rhapsody', 'Queen')
  assert Song('Bohemian Rhapsody', 'Queen') != Song('Another One Bites the Dust', 'Queen')
  assert Song('Bohemian Rhapsody', 'Queen') != Song('Bohemian Rhapsody', 'Queen Latifah')
  assert Song('Bohemian Rhapsody', 'Queen').length() == 17
  assert Song('Little Wing', 'Jimi Hendrix').length() == 11
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)