[node] fix load_handlers. Load directly the function is contains specific handlers

scheme/node.py

@@ -117,6 +117,10 @@ class Node(object):
     def process_pt(self):
         return self._process_pt
 
+    @property
+    def class_instance(self):
+        return self.__process_instance
+
     def isfinal(self) -> bool:
         """
 
@@ -176,7 +180,7 @@ class Node(object):
                 if hasattr(self.__process_instance, 'inputs'):
                     for input_ in self.__process_instance.inputs:
                         input_name, input_type, input_handler = input_
-                        self._handlers[input_name] = input_handler
+                        self._handlers[input_name] = getattr(self.__process_instance, input_handler)
 
         if len(self._handlers) == 0:
             raise ValueError('Fail to init handlers, none defined for ' + str(self._process_pt))
@@ -301,4 +305,4 @@ class ErrorHandler(Node):
                                            error_handler=None)
 
     def _get_error_handler_json(self):
-        return {}
\ No newline at end of file
+        return {}