old_contents: class Transform:
      def __init__(self, number):
          self.number = number
  
      def transform(self, number):
          self.number = number
          new_number = self.number + 1
          return new_number
  
new_contents: class Transform:
      def __init__(self):
          #self.number = number
          pass
  
      def transform(self, number):
          #self.number = number
          #new_number = self.number + 1
          return number + 1
  
subject: Update transformer.py