honor secondary_header flag, return None impl

edosl0util/stream.py

@@ -71,6 +71,8 @@ class SequenceId(object):
 
 
 def default_header_lookup(primary_header):
+    if not primary_header.secondary_header_flag:
+        return None
     return (
         headers.aqua_header_lookup(primary_header) or
         headers.jpss_header_lookup(primary_header)