Address comments on code review

util/names.py

@@ -34,6 +34,27 @@ def parse_robot_username(robot_username):
   return robot_username.split('+', 2)
 
 
+def parse_urn(urn):
+  """ Parses a URN, returning a pair that contains a list of URN
+      namespace parts, followed by the URN's unique ID.
+  """
+  if not urn.startswith('urn:'):
+    return None
+
+  parts = urn[len('urn:'):].split(':')
+  return (parts[0:len(parts) - 1], parts[len(parts) - 1])
+
+
+def parse_single_urn(urn):
+  """ Parses a URN, returning a pair that contains the first
+      namespace part, followed by the URN's unique ID.
+  """
+  result = parse_urn(urn)
+  if result is None or not len(result[0]):
+    return None
+
+  return (result[0][0], result[1])
+
 uuid_generator = lambda: str(uuid4())