docs: Documentation update

Change-Id: I6f916eb822a59e980e8fb1134886c3431755119c
diff --git a/utils/trie/empty-policy.hpp b/utils/trie/empty-policy.hpp
index 404028f..237a647 100644
--- a/utils/trie/empty-policy.hpp
+++ b/utils/trie/empty-policy.hpp
@@ -20,6 +20,8 @@
 #ifndef EMPTY_POLICY_H_
 #define EMPTY_POLICY_H_
 
+/// @cond include_hidden
+
 namespace ns3 {
 namespace ndn {
 namespace ndnSIM {
@@ -76,4 +78,6 @@
 } // ndn
 } // ns3
 
+/// @endcond
+
 #endif // EMPTY_POLICY_H_