Update with comments

Author: luotao1

python/paddle/v2/inference.py

@@ -38,23 +38,26 @@ def __reader_impl__():
 
     def iter_infer_field(self, field, **kwargs):
         for result in self.iter_infer(**kwargs):
-            yield [each_result[field] for each_result in result]
+            yield [
+                each_result[each_field]
+                for each_result in result for each_field in field
+            ]
 
     def infer(self, field='value', **kwargs):
         if not isinstance(field, list) and not isinstance(field, tuple):
             field = [field]
 
-        retv_list = []
-        for each_field in field:
-            retv = None
-            for result in self.iter_infer_field(field=each_field, **kwargs):
-                if retv is None:
-                    retv = [[]] * len(result)
-                for i, item in enumerate(result):
-                    retv[i].append(item)
-            retv = [numpy.concatenate(out) for out in retv]
-            retv_list.append(retv[0] if len(retv) == 1 else retv)
-        return retv_list[0] if len(retv_list) == 1 else retv_list
+        retv = None
+        for result in self.iter_infer_field(field=field, **kwargs):
+            if retv is None:
+                retv = [[]] * len(result)
+            for i, item in enumerate(result):
+                retv[i].append(item)
+        retv = [numpy.concatenate(out) for out in retv]
+        if len(retv) == 1:
+            return retv[0]
+        else:
+            return retv
 
 
 def infer(output_layer, parameters, input, feeding=None, field='value'):