input: Write a function to determine if it is possible to create a class in Python which matches the given criteria. The class should be named Song and should have two instance variables, title and artist, and three methods, str(), eq(), and length(). If it is possible, return True; otherwise, return False. If the input criteria is empty, return True.
  assert test_song_class('''
  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)''')==True
  
  assert test_song_class('''
  class Song:
      def __init__(self, title):
          self.title = title''')==False
  
  assert test_song_class('''
  class Song:
      def __init__(self, title, artist):
          self.title = title''')==False
  
  assert test_song_class('''
  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''')==False
  
  assert test_song_class('')==True
output: def test_song_class(criteria):
      if not criteria:
          return True
      
      try:
          exec(criteria)
          song_instance = Song("Test Title", "Test Artist")
          
          if not hasattr(song_instance, 'title') or not hasattr(song_instance, 'artist'):
              return False
          
          if not callable(getattr(song_instance, '__str__', None)):
              return False
          
          if not callable(getattr(song_instance, '__eq__', None)):
              return False
          
          if not callable(getattr(song_instance, 'length', None)):
              return False
          
          return True
      except:
          return False