old_contents: import sys
  
  class A:
      def __init__(self, x, y):
          self.x = x
          self.y = y
  
  class B:
      __slots__ = ('x', 'y')
  
      def __init__(self, x, y):
          self.x = x
          self.y = y
  
  a = A(1, 2)
  assert '__dict__' in dir(a)
  
  # 'b' will have a lower memory footprint than 'a' due to the use of __slots__:
  b = B(1, 2)
  assert '__dict__' not in dir(b)
  
new_contents: import sys
  
  class A:
      def __init__(self, x, y):
          self.x = x
          self.y = y
  
  class B:
      __slots__ = ('x', 'y')
  
      def __init__(self, x, y):
          self.x = x
          self.y = y
  
  a = A(1, 2)
  assert '__dict__' in dir(a)
  
  # 'b' will have a lower memory footprint and provide faster attribute access
  # than 'a' due to the use of __slots__:
  b = B(1, 2)
  assert '__dict__' not in dir(b)
  
subject: Improve a comment in 24-slots.py.