[Exp PyROOT] Document the use of the pythonizor helpers, invoked from Python

bindings/pyroot_experimental/PyROOT/CMakeLists.txt

@@ -20,7 +20,7 @@ set(sources
   src/TFilePyz.cxx
   src/TTreePyz.cxx
   src/GenericPyz.cxx
-  src/Helpers.cxx
+  src/PyzPythonHelpers.cxx
   src/PyzCppHelpers.cxx
 )
 

bindings/pyroot_experimental/PyROOT/src/Helpers.cxx → bindings/pyroot_experimental/PyROOT/src/PyzPythonHelpers.cxx

@@ -9,6 +9,14 @@
  * For the list of contributors see $ROOTSYS/README/CREDITS.             *
  *************************************************************************/
 
+/**
+
+Set of helper functions that are invoked from the pythonizors, on the
+Python side. For that purpose, they are included in the interface of the
+PyROOT extension module.
+
+*/
+
 #include "CPyCppyy.h"
 #include "CPPInstance.h"
 #include "PyROOTPythonize.h"