+ /**
+ * @brief Returns the number of *non-empty* entries in the tree, viz. the
+ * number of nodes in the tree that have an action mapped to them
+ */
+ size_t get_num_entries() const { return !empty() ? (nodes_.size() - 1) : static_cast<size_t>(0); }
+
+ /**
+ * @brief Returns the number of nodes in the tree, including the root node
+ */
+ size_t get_num_nodes() const { return nodes_.size(); }
+