input: Write a function to create a class named 'Song' with instance variables 'title' and 'artist', and methods 'str()', 'eq()', and 'length()'. The 'str()' method should return a string representation of the song combining the title and artist, the 'eq()' method should compare two songs based on their title and artist, and the 'length()' method should return the length of the song title. If the class meets these criteria, return True, otherwise return False.
  
  assert Song("Hey Jude", "The Beatles").__str__() == 'Title: Hey Jude\nArtist: The Beatles'
  assert Song("Hey Jude", "The Beatles").__eq__(Song("Hey Jude", "The Beatles")) == True
  assert Song("Hey Jude", "The Beatles").__eq__(Song("Like a Rolling Stone", "Bob Dylan")) == False
  assert Song("Hey Jude", "The Beatles").length() == 8
  assert Song("","Unknown artist").length() == 0
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)