[Bug Fix] Fix Heterogenous graph save crash when some edge type names are identical. (#1751)

* Fix hetero serialize

* Add test case
y
Co-authored-by: Ubuntu <ubuntu@ip-172-31-51-214.ec2.internal>
Co-authored-by: Jinjing Zhou <VoVAllen@users.noreply.github.com>

python/dgl/data/heterograph_serialize.py

@@ -35,7 +35,7 @@ class HeteroGraphData(ObjectBase):
     def create(g):
         edata_list = []
         ndata_list = []
-        for etype in g.etypes:
+        for etype in g.canonical_etypes:
             edata_list.append(tensor_dict_to_ndarray_dict(g.edges[etype].data))
         for ntype in g.ntypes:
             ndata_list.append(tensor_dict_to_ndarray_dict(g.nodes[ntype].data))

tests/compute/test_serialize.py

@@ -223,6 +223,17 @@ def create_heterographs(index_dtype):
     g = dgl.hetero_from_relations([g_x, g_y])
     return [g, g_x, g_y]
 
+def create_heterographs2(index_dtype):
+    g_x = dgl.graph(([0, 1, 2], [1, 2, 3]), 'user',
+                    'follows', index_dtype=index_dtype, restrict_format='any')
+    g_y = dgl.graph(([0, 2], [2, 3]), 'user', 'knows', index_dtype=index_dtype, restrict_format='csr')
+    g_z = dgl.bipartite(([0, 1, 3], [2, 3, 4]), 'user', 'knows', 'knowledge', index_dtype=index_dtype)
+    g_x.nodes['user'].data['h'] = F.randn((4, 3))
+    g_x.edges['follows'].data['w'] = F.randn((3, 2))
+    g_y.nodes['user'].data['hh'] = F.ones((4, 5))
+    g_y.edges['knows'].data['ww'] = F.randn((2, 10))
+    g = dgl.hetero_from_relations([g_x, g_y, g_z])
+    return [g, g_x, g_y]
 
 def test_deserialize_old_heterograph_file():
     path = os.path.join(
@@ -251,11 +262,15 @@ def test_serialize_heterograph():
     f = tempfile.NamedTemporaryFile(delete=False)
     path = f.name
     f.close()
-    g_list0 = create_heterographs("int64") + create_heterographs("int32")
+    g_list0 = create_heterographs2("int64") + create_heterographs2("int32")
     save_graphs(path, g_list0)
 
     g_list, _ = load_graphs(path)
     assert g_list[0].idtype == F.int64
+    assert len(g_list[0].canonical_etypes) == 3
+    for i in range(len(g_list0)):
+        for j, etypes in enumerate(g_list0[i].canonical_etypes):
+            assert g_list[i].canonical_etypes[j] == etypes
     assert g_list[1].restrict_format() == 'any'
     assert g_list[2].restrict_format() == 'csr'
     assert g_list[3].idtype == F.int32