input: 
  class Song:
      """A class that represents a song with a title and artist.
  
      >>> song1 = Song("Shape of You", "Ed Sheeran")
      >>> str(song1)
      'Title: Shape of You\nArtist: Ed Sheeran'
      >>> song2 = Song("Shape of You", "Ed Sheeran")
      >>> song1 == song2
      True
      >>> song1.length()
      11
      """
      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)
  
output:     def length(self):
          return len(self.title)