Fix typo, NodeExport was not using is_input and is_output

aidge_core/export_utils/node_export.py

@@ -143,8 +143,8 @@ class ExportNode(ABC):
         # TODO : this check doesn't work if we export a subgraph !
         # Maybe we need to add the graph we want to export as parameter !
         # Actually may be mandatory for memory manager ...
-        self.attributes["is_input"] = len(self.node.get_parents()) == 0
-        self.attributes["is_output"] = len(self.node.get_children()) == 0
+        self.attributes["is_input"] = is_input
+        self.attributes["is_output"] = is_output
         self.inputs = []
         self.outputs = []