old_contents: """Objects for users."""
  
  __all__ = [
      "User",
      "Users",
  ]
  
  from . import (
      check,
      Object,
      ObjectField,
      ObjectSet,
      ObjectType,
  )
  
  
  class UsersType(ObjectType):
      """Metaclass for `Users`."""
  
      def __iter__(cls):
          return map(cls._object, cls._handler.read())
  
      def create(cls, username, email, password, *, is_superuser=False):
          data = cls._handler.create(
              username=username, email=email, password=password,
              is_superuser='1' if is_superuser else '0')
          return cls._object(data)
  
  
  class Users(ObjectSet, metaclass=UsersType):
      """The set of users."""
  
      @classmethod
      def read(cls):
          return cls(cls)
  
  
  class User(Object):
      """A user."""
  
      username = ObjectField.Checked(
          "username", check(str), check(str))
      email = ObjectField.Checked(
          "email", check(str), check(str))
      is_admin = ObjectField.Checked(
          "is_superuser", check(bool), check(bool))
  
new_contents: """Objects for users."""
  
  __all__ = [
      "User",
      "Users",
  ]
  
  from . import (
      check,
      Object,
      ObjectField,
      ObjectSet,
      ObjectType,
  )
  
  
  class UsersType(ObjectType):
      """Metaclass for `Users`."""
  
      def __iter__(cls):
          return map(cls._object, cls._handler.read())
  
      def create(cls, username, password, *, email=None, is_superuser=False):
          if email is None:
              email = "%s@null.maas.io" % username
          data = cls._handler.create(
              username=username, email=email, password=password,
              is_superuser='1' if is_superuser else '0')
          return cls._object(data)
  
  
  class Users(ObjectSet, metaclass=UsersType):
      """The set of users."""
  
      @classmethod
      def read(cls):
          return cls(cls)
  
  
  class User(Object):
      """A user."""
  
      username = ObjectField.Checked(
          "username", check(str), check(str))
      email = ObjectField.Checked(
          "email", check(str), check(str))
      is_superuser = ObjectField.Checked(
          "is_superuser", check(bool), check(bool))
  
subject: Change to is_superuser and make email optional.