update docstring

gtsam/hybrid/HybridBayesNet.h

@@ -209,7 +209,8 @@ class GTSAM_EXPORT HybridBayesNet : public BayesNet<HybridConditional> {
    * @brief Prune the Bayes Net such that we have at most maxNrLeaves leaves.
    *
    * @param maxNrLeaves Continuous values at which to compute the error.
-   * @param removeDeadModes
+   * @param removeDeadModes Flag to enable removal of modes which only have a
+   * single possible assignment.
    * @return A pruned HybridBayesNet
    */
   HybridBayesNet prune(size_t maxNrLeaves, bool removeDeadModes = false) const;