old_contents: class ConfigItem(object):
      """The configuration item which may be bound with a instance.
  
      :param name: the property name.
      :param namespace: optional. the name of the attribute which contains all
                        configuration nested in the instance.
      :param default: optional. the value which be provided while the
                      configuration item has been missed.
      :param required: optional. if this paramater be ``True`` , getting missed
                       configuration item without default value will trigger a
                       ``RuntimeError`` .
      """
  
      def __init__(self, name, namespace="config", default=None, required=False):
          self.name = self.name
          self.namespace = namespace
          self.default = default
          self.is_required = required
  
      def __repr__(self):
          template = "ConfigItem(%r, namespace=%r, default=%r, required=%r)"
          return template % (self.name, self.name, self.default, self.required)
  
      def __get__(self, instance, owner):
          if instance is None:
              return self
          namespace = self._namespace(instance)
          if self.name not in namespace and self.required:
              raise RuntimeError("missing %s['%s'] in %r" %
                                 (self.namespace, self.name, instance))
          return namespace.get(self.name, self.default)
  
      def __set__(self, instance, value):
          namespace = self._namespace(instance)
          namespace[self.name] = value
  
      def _namespace(self, instance):
          """Gets exists namespace or creates it."""
          if not hasattr(instance, self.namespace):
              setattr(instance, self.namespace, {})
          return getattr(instance, self.namespace)
  
new_contents: class ConfigItem(object):
      """The configuration item which may be bound with a instance.
  
      :param name: the property name.
      :param namespace: optional. the name of the attribute which contains all
                        configuration nested in the instance.
      :param default: optional. the value which be provided while the
                      configuration item has been missed.
      :param required: optional. if this paramater be ``True`` , getting missed
                       configuration item without default value will trigger a
                       ``RuntimeError`` .
      """
  
      def __init__(self, name, namespace="config", default=None, required=False):
          self.name = name
          self.namespace = namespace
          self.default = default
          self.is_required = required
  
      def __repr__(self):
          template = "ConfigItem(%r, namespace=%r, default=%r, required=%r)"
          return template % (self.name, self.name, self.default, self.required)
  
      def __get__(self, instance, owner):
          if instance is None:
              return self
          namespace = self._namespace(instance)
          if self.name not in namespace and self.required:
              raise RuntimeError("missing %s['%s'] in %r" %
                                 (self.namespace, self.name, instance))
          return namespace.get(self.name, self.default)
  
      def __set__(self, instance, value):
          namespace = self._namespace(instance)
          namespace[self.name] = value
  
      def _namespace(self, instance):
          """Gets exists namespace or creates it."""
          if not hasattr(instance, self.namespace):
              setattr(instance, self.namespace, {})
          return getattr(instance, self.namespace)
  
subject: fix up a typo in utilities.