code: def get_value(self, instance, *bits):
          '''Retrieve the value :class:`Field` from a :class:`StdModel`
  ``instance``.
  
  :param instance: The :class:`StdModel` ``instance`` invoking this function.
  :param bits: Additional information for nested fields which derives from
      the :ref:`double underscore <tutorial-underscore>` notation.
  :return: the value of this :class:`Field` in the ``instance``. can raise
      :class:`AttributeError`.
  
  This method is used by the :meth:`StdModel.get_attr_value` method when
  retrieving values form a :class:`StdModel` instance.
  '''
          if bits:
              raise AttributeError
          else:
              return getattr(instance, self.attnamef get_value(self, instance, *bits):
          '''Retrieve the value :class:`Field` from a :class:`StdModel`
  ``instance``.
  
  :param instance: The :class:`StdModel` ``instance`` invoking this function.
  :param bits: Additional information for nested fields which derives from
      the :ref:`double underscore <tutorial-underscore>` notation.
  :return: the value of this :class:`Field` in the ``instance``. can raise
      :class:`AttributeError`.
  
  This method is used by the :meth:`StdModel.get_attr_value` method when
  retrieving values form a :class:`StdModel` instance.
  '''
          if bits:
              raise AttributeError
          else:
              return getattr(instance, self.attname)
docs: Retrieve the value :class:`Field` from a :class:`StdModel`
  ``instance``.
  
  :param instance: The :class:`StdModel` ``instance`` invoking this function.
  :param bits: Additional information for nested fields which derives from
      the :ref:`double underscore <tutorial-underscore>` notation.
  :return: the value of this :class:`Field` in the ``instance``. can raise
      :class:`AttributeError`.
  
  This method is used by the :meth:`StdModel.get_attr_value` method when
  retrieving values form a :class:`StdModel` instance.