add serialization to HybridGaussianProductFactor

gtsam/hybrid/HybridGaussianProductFactor.h

@@ -115,6 +115,16 @@ class GTSAM_EXPORT HybridGaussianProductFactor
   HybridGaussianProductFactor removeEmpty() const;
 
   ///@}
+
+ private:
+#ifdef GTSAM_ENABLE_BOOST_SERIALIZATION
+  /** Serialization function */
+  friend class boost::serialization::access;
+  template <class Archive>
+  void serialize(Archive& ar, const unsigned int /*version*/) {
+    ar& BOOST_SERIALIZATION_BASE_OBJECT_NVP(Base);
+  }
+#endif
 };
 
 // Testable traits

gtsam/hybrid/tests/testSerializationHybrid.cpp

@@ -59,6 +59,9 @@ BOOST_CLASS_EXPORT_GUID(HybridGaussianFactor::FactorValuePairs::Leaf,
 BOOST_CLASS_EXPORT_GUID(HybridGaussianFactor::FactorValuePairs::Choice,
                         "gtsam_HybridGaussianFactor_Factors_Choice");
 
+BOOST_CLASS_EXPORT_GUID(GaussianFactorGraphValuePair,
+                        "gtsam_GaussianFactorGraphValuePair");
+
 BOOST_CLASS_EXPORT_GUID(HybridGaussianConditional,
                         "gtsam_HybridGaussianConditional");
 BOOST_CLASS_EXPORT_GUID(HybridGaussianConditional::Conditionals,