private static String createJsonInput(String modelPath, Map<String, TensorType> inputTypes) throws IOException {
        ByteArrayOutputStream out = new ByteArrayOutputStream();
        JsonGenerator g = new JsonFactory().createGenerator(out, JsonEncoding.UTF8);
        g.writeStartObject();
        g.writeStringField("model", modelPath);
        g.writeObjectFieldStart("inputs");
        for (Map.Entry<String, TensorType> input : inputTypes.entrySet()) {
            g.writeStringField(input.getKey(), input.getValue().toString());
        }
        g.writeEndObject();
        g.writeEndObject();
        g.close();
        return out.toString();
    }
Defers to 'vespa-analyze-onnx-model' to determine the output type given
a set of inputs. For situations with symbolic dimension sizes that can't
easily be determined.

@author lesters
config-model/src/main/java/com/yahoo/vespa/model/ml/OnnxModelProbe.java