add 'raise NotImplementedError' in alg_type

Raise NotImplementedError when alg_type is not set as one of ['bi', 'kgat', 'gcn', 'graphsage'], in order to solve some errors like 'no ua_embeddings'.

Model/KGAT.py

@@ -158,14 +158,17 @@ def _build_weights(self):
         return all_weights
 
     def _build_model_phase_I(self):
-        if self.alg_type in ['bi']:
+        if self.alg_type in ['bi', 'kgat']:
             self.ua_embeddings, self.ea_embeddings = self._create_bi_interaction_embed()
 
         elif self.alg_type in ['gcn']:
             self.ua_embeddings, self.ea_embeddings = self._create_gcn_embed()
 
         elif self.alg_type in ['graphsage']:
             self.ua_embeddings, self.ea_embeddings = self._create_graphsage_embed()
+        else:
+            print('please check the the alg_type argument, which should be bi, kgat, gcn, or graphsage.')
+            raise NotImplementedError
 
         self.u_e = tf.nn.embedding_lookup(self.ua_embeddings, self.users)
         self.pos_i_e = tf.nn.embedding_lookup(self.ea_embeddings, self.pos_items)