input: Write a function to create a Python 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 that includes the title and artist of the song. The eq() method should check if two songs are equal by comparing their title and artist. The length() method should return the number of characters in the song's title. If the given input is valid, return True; otherwise, return False.
  
  
  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', 'title', 'artist') == 'Title: title\nArtist: artist'
  assert __eq__('Song', Song('Song1', 'Artist1'), Song('Song1', 'Artist1')) == True
  assert __eq__('Song', Song('Song1', 'Artist1'), Song('Song2', 'Artist2')) == False
  assert length('Song', 'Title') == 5
  assert length('Song', '') == 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.artist == other.artist and self.title == other.title
  
      def length(self):
          return len(self.title)