old_contents: # -*- coding: utf-8 -*-
  
  
  class BasicSchema(object):
      pass
  
new_contents: # -*- coding: utf-8 -*-
  
  import collections
  
  
  Type = collections.namedtuple('Type', ['name', '_type', 'examples'])
  
  
  class SchemaMeta(type):
      def __init__(self, name, parents, attrs):
          super().__init__(name, parents, attrs)
          assert isinstance(attrs['fields'])
          for field in attrs['fields']:
              assert isinstance(field, Type)
  
  
  class BasicSchema(object, metaclass=SchemaMeta):
      fields = []
  
subject: Expand schema