'Find the delete_<entity_type> method.
Searches through the [identity_api, resource_api, assignment_api]
managers for a method called delete_<entity_type> and returns the first
one.'

def _delete_entity(self, entity_type):

    f = getattr(self.identity_api, ('delete_%s' % entity_type), None)
    if (f is None):
        f = getattr(self.resource_api, ('delete_%s' % entity_type), None)
    if (f is None):
        f = getattr(self.assignment_api, ('delete_%s' % entity_type))
    return f
