Prefix smart parser lacks the prefix_length attribute
The prefix smart parser lacks the prefix_length attribute.

Perhaps we could use the list of attributes in backend.py to populate the attribute lists in the smart parser classes?

diff --git a/nipap/nipap/smart_parsing.py b/nipap/nipap/smart_parsing.py
index 5dc510f3..d910567a 100644
--- a/nipap/nipap/smart_parsing.py
+++ b/nipap/nipap/smart_parsing.py
@@ -406,6 +406,7 @@ class PrefixSmartParser(SmartParser):
         'order_id': True,
         'pool': True,
         'prefix': True,
+        'prefix_length': True,
         'status': True,
         'total_addresses': True,
         'type': True,
['nipap/nipap/smart_parsing.py']