public static OperationIndex of(Model model) {
        return model.getKnowledge(OperationIndex.class, OperationIndex::new);
    }
Index of operation IDs to their resolved input, output, and error
structures.

<p>This index performs no validation that the input, output, and
errors actually reference valid structures. Such operation inputs,
outputs, and errors may be discarded as if they do not exist.
smithy-model/src/main/java/software/amazon/smithy/model/knowledge/OperationIndex.java