input: Write a function to create a class Song in Python 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 title and artist, the __eq__() method should compare two Song objects based on their title and artist, and the length() method should return the length of the song title. 
  
  assert str(Song("Bohemian Rhapsody", "Queen")) == 'Title: Bohemian Rhapsody\nArtist: Queen'
  assert Song("Bohemian Rhapsody", "Queen") == Song("Bohemian Rhapsody", "Queen")
  assert Song("Bohemian Rhapsody", "Queen") != Song("Bohemian Rhapsody", "Freddie Mercury")
  assert Song("Bohemian Rhapsody", "Queen").length() == 16
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.title == other.title and self.artist == other.artist
  
      def length(self):
          return len(self.title)