'Register a callback for a resource type.
:param callback: the callback. It must raise or return NeutronObject.
:param resource_type: must be a valid resource type.'

def register(self, callback, resource_type):

    LOG.debug('Registering    callback    for    %s', resource_type)
    _validate_resource_type(resource_type)
    self._add_callback(callback, resource_type)
