new_contents: 
  
  class Change(object):
      def __init__(self, name):
          self.name = name
  
      @classmethod
      def from_dict(self, data):
          return Change(data['name'])
  
      def to_dict(self):
          return {'name': self.name}
  
      def __str__(self):
          return "<Change name='%s'>" % self.name
  
subject: Add basic Change model