'Helper assertion that a pair of xblocks have a certain kind of
relationship with one another.'

def assertBlockPairIsRelationship(self, xblock1, xblock2, relationships, relationship_type):

    relationship_pairs = self._extract_relationship_pairs(relationships, relationship_type)
    location_pair = self._extract_location_pair(xblock1, xblock2)
    self.assertIn(location_pair, relationship_pairs)
