docs: Documentation update

Change-Id: I6f916eb822a59e980e8fb1134886c3431755119c
diff --git a/model/cs/custom-policies/freshness-policy.hpp b/model/cs/custom-policies/freshness-policy.hpp
index 8963bd7..415ab0b 100644
--- a/model/cs/custom-policies/freshness-policy.hpp
+++ b/model/cs/custom-policies/freshness-policy.hpp
@@ -20,6 +20,8 @@
 #ifndef FRESHNESS_POLICY_H_
 #define FRESHNESS_POLICY_H_
 
+/// @cond include_hidden
+
 #include "ns3/ndnSIM/model/ndn-common.hpp"
 
 #include <boost/intrusive/options.hpp>
@@ -166,4 +168,6 @@
 } // ndn
 } // ns3
 
+/// @endcond
+
 #endif // LIFETIME_STATS_POLICY_H