Address comments

gtsam/hybrid/HybridEliminationTree.h

@@ -23,6 +23,9 @@
 
 namespace gtsam {
 
+/**
+ * Elimination Tree type for Hybrid
+ */
 class GTSAM_EXPORT HybridEliminationTree
     : public EliminationTree<HybridBayesNet, HybridFactorGraph> {
  public:

gtsam/hybrid/HybridFactorGraph.h

@@ -62,6 +62,12 @@ struct EliminationTraits<HybridFactorGraph> {
   }
 };
 
+/**
+ * Hybrid Factor Graph
+ * -----------------------
+ * This is the linear version of a hybrid factor graph. Everything inside needs
+ * to be hybrid factor or hybrid conditional.
+ */
 class HybridFactorGraph : public FactorGraph<HybridFactor>,
                           public EliminateableFactorGraph<HybridFactorGraph> {
  public: