'get_many returns nothing for the dummy cache backend'

def test_get_many(self):

    self.cache.set(u'a', u'a')
    self.cache.set(u'b', u'b')
    self.cache.set(u'c', u'c')
    self.cache.set(u'd', u'd')
    self.assertEqual(self.cache.get_many([u'a', u'c', u'd']), {})
    self.assertEqual(self.cache.get_many([u'a', u'b', u'e']), {})
