fix: change default

src/anemoi/graphs/create.py

@@ -108,7 +108,7 @@ def post_process(self, graph: HeteroData) -> HeteroData:
         Post-processors are applied in the order they are specified in the configuration.
         Each post-processor should implement an `update_graph` method that takes and returns a HeteroData object.
         """
-        for processor in self.config.get("post_processors", {}):
+        for processor in self.config.get("post_processors", []):
             graph = instantiate(processor).update_graph(graph)
 
         return graph