input: Write a function to create a 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 with the title and artist, the `eq()` method should compare two instances of the Song class based on their title and artist, and the `length()` method should return the length of the title. If the function is implemented correctly, it should pass the provided assert statements.
  
  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 Song("Bohemian Rhapsody", "Queen") == Song("Bohemian Rhapsody", "Queen")
  assert Song("Bohemian Rhapsody", "Queen") != Song("Stairway to Heaven", "Led Zeppelin")
  assert Song("Bohemian Rhapsody", "Queen").length() == 17
output: 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)