def _get_default(cls, attribute):
        """Return the default value for `attribute`.

        If no default is specified in this style, get the default from the
        nearest superclass.
        If `attribute` is not supported, raise a :class:`KeyError`."""
        try:
            for klass in cls.__mro__:
                if attribute in klass._attributes:
                    return klass._attributes[attribute].default_value
        except AttributeError:
            raise KeyError("No attribute '{}' in {}".format(attribute, cls))
Return the default value for `attribute`.

        If no default is specified in this style, get the default from the
        nearest superclass.
        If `attribute` is not supported, raise a :class:`KeyError`.