Drop deprecated `iteritems` in pandas

app.py

@@ -160,7 +160,7 @@ def try_validate(m_id, ppl, dataset_id, dataset_config, dataset_split, column_ma
 
 def try_submit(m_id, d_id, config, split, column_mappings, local):
     label_mapping = {}
-    for i, label in column_mappings["Model Prediction Labels"].iteritems():
+    for i, label in column_mappings["Model Prediction Labels"].items():
         label_mapping.update({str(i): label})
 
     # TODO: Set column mapping for some dataset such as `amazon_polarity`