Improve type of function callbacks in register_upgrade_function and register_downgrade_function (#1445)

Author: JeanChristopheMorinPerso

src/py-opentimelineio/opentimelineio-bindings/otio_bindings.cpp

@@ -2,6 +2,7 @@
 // Copyright Contributors to the OpenTimelineIO project
 
 #include <pybind11/pybind11.h>
+#include <pybind11/functional.h>
 #include "otio_anyDictionary.h"
 #include "otio_anyVector.h"
 #include "otio_bindings.h"
@@ -71,13 +72,12 @@ static void register_python_type(py::object class_object,
 
 static bool register_upgrade_function(std::string const& schema_name,
                                       int version_to_upgrade_to,
-                                      py::object const& upgrade_function_obj) {
+                                      std::function<void(AnyDictionaryProxy*)> const& upgrade_function_obj) {
     std::function<void (AnyDictionary* d)> upgrade_function =  [upgrade_function_obj](AnyDictionary* d) {
         py::gil_scoped_acquire acquire;
 
         auto ptr = d->get_or_create_mutation_stamp();
-        py::object dobj = py::cast((AnyDictionaryProxy*)ptr);
-        upgrade_function_obj(dobj);
+        upgrade_function_obj((AnyDictionaryProxy*)ptr);
     };
 
     // further discussion required about preventing double registering
@@ -112,16 +112,15 @@ static bool
 register_downgrade_function(
         std::string const& schema_name,
         int version_to_downgrade_from,
-        py::object const& downgrade_function_obj) 
+        std::function<void(AnyDictionaryProxy*)> const& downgrade_function_obj)
 {
     std::function<void (AnyDictionary* d)> downgrade_function = ( 
             [downgrade_function_obj](AnyDictionary* d) 
             {
                 py::gil_scoped_acquire acquire;
 
                 auto ptr = d->get_or_create_mutation_stamp();
-                py::object dobj = py::cast((AnyDictionaryProxy*)ptr);
-                downgrade_function_obj(dobj);
+                downgrade_function_obj((AnyDictionaryProxy*)ptr);
             }
     );