TypeRuntimeWiring.newTypeWiring("Query")
        .dataFetcher(
            "myField",
            environment -> {
              String myId = environment.getArgument("myId");
              
              // it's OK if this is null, because the keyContext is allowed to be null?
              Integer myKeyContext = getNullableKeyContext(...);

              return environment.getDataLoader("myLoader").load(myId, myKeyContext);
            })
        .build();