input: Write a function to define 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.
  
  
  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("Shape of You", "Ed Sheeran"))=='Title: Shape of You\nArtist: Ed Sheeran'
  assert Song("Shape of You", "Ed Sheeran")==Song("Shape of You", "Ed Sheeran")
  assert Song("Shape of You", "Ed Sheeran")!=Song("Bohemian Rhapsody", "Queen")
  assert Song("Shape of You", "Ed Sheeran").length()==11
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.artist == other.artist and self.title == other.title
  
      def length(self):
          return len(self.title)