Make test_net_info a bit more robust.

infra_libs/ts_mon/common/metric_store.py

Index: infra_libs/ts_mon/common/metric_store.py
diff --git a/infra_libs/ts_mon/common/metric_store.py b/infra_libs/ts_mon/common/metric_store.py
index a555e3cb9a8bf9923d05d14c301e539a2d390b13..4d21feeabd964d1a1a1354f0f77bbab14eb355d9 100644
--- a/infra_libs/ts_mon/common/metric_store.py
+++ b/infra_libs/ts_mon/common/metric_store.py
@@ -4,6 +4,7 @@
 
 import collections
 import copy
+import itertools
 import threading
 import time
 
@@ -204,7 +205,8 @@ class TargetFieldsValues(object):
       values = copy.copy(self._values)
     for target_fields, fields_values in values.iteritems():
       target = copy.copy(self._store._state.target)
-      target.update({k: v for k, v in target_fields})
+      if target_fields:
+        target.update({k: v for k, v in target_fields})
       yield target, fields_values
 
 
@@ -246,6 +248,10 @@ class InProcessMetricStore(MetricStore):
   def get(self, name, fields, target_fields, default=None):
     return self._entry(name).get_value(fields, target_fields, default)
 
+  def iter_field_values(self, name):
+    return itertools.chain.from_iterable(
+        x.iteritems() for _, x in self._entry(name).values.iter_targets())
+
   def get_all(self):
     # Make a copy of the metric values in case another thread (or this
     # generator's consumer) modifies them while we're iterating.