Update graph_utilities.py

Make graphfcn registry a dict

swmmanywhere/graph_utilities.py

@@ -121,9 +121,24 @@ def add_graphfcn(self,
         node_attributes = node_attributes.union(self.adds_node_attributes)
         return edge_attributes, node_attributes
 
-class GraphFunctionRegistry: 
+class GraphFunctionRegistry(dict): 
     """Registry object.""" 
-    pass
+
+    def register(self, cls):
+        """Register a graph function."""
+        if cls.__name__ in self:
+            raise ValueError(f"{cls.__name__} already in the graph functions registry!")
+
+        self[cls.__name__] = cls()
+        return cls
+
+    def __getattr__(self, name):
+        """Get a graph function from the graphfcn dict."""
+        try:
+            return self[name]
+        except KeyError:
+            raise AttributeError(f"{name} NOT in the graph functions registry!")
+
 
 graphfcns = GraphFunctionRegistry()
 
@@ -136,7 +151,7 @@ def register_graphfcn(cls) -> Callable:
     Returns:
         cls (Callable): The same class
     """
-    setattr(graphfcns, cls.__name__, cls())
+    graphfcns.register(cls)
     return cls
 
 def get_osmid_id(data: dict) -> Hashable: