<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def get(self):
 """List existing config namespaces and their items"""

        namespaces = db.ConfigNamespace.order_by(
            ConfigNamespace.sort_order,
            ConfigNamespace.name
        ).all()

        return self.make_response({
            'message': None,
            'namespaces': namespaces
        }, HTTP.OK)