input: 
  class SongTest:
      """Test if a class Song can be instantiated with title and artist, and if its methods
      return the expected values for __str__, __eq__, and length.
      >>> song1 = Song("Bohemian Rhapsody", "Queen")
      >>> str(song1)
      'Title: Bohemian Rhapsody\nArtist: Queen'
      >>> song2 = Song("Bohemian Rhapsody", "Queen")
      >>> song1 == song2
      True
      >>> song1.length()
      17
      >>> song3 = Song("Stairway to Heaven", "Led Zeppelin")
      >>> song1 == song3
      False
      >>> song3.length()
      18
      """
  
output:     
  class Song:
      def __init__(self, title: str, artist: str):
          self.title = title
          self.artist = artist
  
      def __str__(self) -> str:
          return f'Title: {self.title}\nArtist: {self.artist}'
  
      def __eq__(self, other: 'Song') -> bool:
          return self.title == other.title and self.artist == other.artist
  
      def length(self) -> int:
          return len(self.title) + len(self.artist)
  