'Return a single volume type item.'

def show(self, req, id):

    context = req.environ['cinder.context']
    if ((id is not None) and (id == 'default')):
        vol_type = volume_types.get_default_volume_type()
        if (not vol_type):
            msg = _('Default    volume    type    can    not    be    found.')
            raise exception.VolumeTypeNotFound(message=msg)
        req.cache_resource(vol_type, name='types')
    else:
        vol_type = volume_types.get_volume_type(context, id)
        req.cache_resource(vol_type, name='types')
    return self._view_builder.show(req, vol_type)
