private Model getModel() {
        return Objects.requireNonNull(model.get(), "The dereferenced WeakReference<Model> is null");
    }
Gets the mapping of {@link MemberShape} to {@link ContextParamTrait} for the operation.

@param operation The operation shape.
@return The mapping of operation's {@link MemberShape} to {@link ContextParamTrait}.
smithy-rules-engine/src/main/java/software/amazon/smithy/rulesengine/traits/ContextIndex.java