Add Schema::leaftypeName

Will be sued in the upcoming describe command.

Change-Id: I9ddecf8d3da1f82e8ce671210d51f31f895a9d27
diff --git a/src/schema.hpp b/src/schema.hpp
index 89a100c..ea0deba 100644
--- a/src/schema.hpp
+++ b/src/schema.hpp
@@ -77,6 +77,7 @@
     virtual const std::set<std::string> listKeys(const schemaPath_& location, const ModuleNodePair& node) const = 0;
     virtual yang::LeafDataTypes leafType(const schemaPath_& location, const ModuleNodePair& node) const = 0;
     virtual yang::LeafDataTypes leafType(const std::string& path) const = 0;
+    virtual std::optional<std::string> leafTypeName(const std::string& path) const = 0;
     virtual yang::LeafDataTypes leafrefBaseType(const schemaPath_& location, const ModuleNodePair& node) const = 0;
     virtual yang::LeafDataTypes leafrefBaseType(const std::string& path) const = 0;
     virtual std::string leafrefPath(const std::string& leafrefPath) const = 0;