Make get_variable_{categories,features} return np.ndarray

miplearn/problems/tsp.py

@@ -80,10 +80,6 @@ class TravelingSalesmanInstance(Instance):
             )
         return model
 
-    @overrides
-    def get_variable_categories(self) -> Dict[str, str]:
-        return {f"x[{e}]": f"x[{e}]" for e in self.edges}
-
     @overrides
     def find_violated_lazy_constraints(
         self,