Fix citation data loading (#2421)

Co-authored-by: Ubuntu <ubuntu@ip-172-31-57-25.ec2.internal>

python/dgl/data/citation_graph.py

@@ -171,13 +171,15 @@ class CitationGraphDataset(DGLBuiltinDataset):
         graphs, _ = load_graphs(str(graph_path))
 
         info = load_info(str(info_path))
-        self._g = graphs[0]
+        graph = graphs[0]
+        self._g = graph
+        # for compatability
         graph = graph.clone()
-        graph.pop('train_mask')
-        graph.pop('val_mask')
-        graph.pop('test_mask')
-        graph.pop('feat')
-        graph.pop('label')
+        graph.ndata.pop('train_mask')
+        graph.ndata.pop('val_mask')
+        graph.ndata.pop('test_mask')
+        graph.ndata.pop('feat')
+        graph.ndata.pop('label')
         graph = to_networkx(graph)
         self._graph = nx.DiGraph(graph)
 

python/dgl/data/dgl_dataset.py

@@ -4,6 +4,7 @@
 from __future__ import absolute_import
 
 import os, sys, hashlib
+import traceback
 import abc
 from .utils import download, extract_archive, get_download_dir, makedirs
 from ..utils import retry_method_with_fix
@@ -170,6 +171,7 @@ class DGLDataset(object):
             except:
                 load_flag = False
                 if self.verbose:
+                    print(traceback.format_exc())
                     print('Loading from cache failed, re-processing.')
 
         if not load_flag: