Explanation payloadExpl = function.explain(doc, field, scorer.payloadsSeen, scorer.payloadScore);
payloadExpl.setValue(scorer.getPayloadScore());
// combined
ComplexExplanation result = new ComplexExplanation();
if (includeSpanScore) {
result.addDetail(expl);
result.addDetail(payloadExpl);
result.setValue(expl.getValue() * payloadExpl.getValue());
result.setDescription("btq, product of:");
} else {
result.addDetail(payloadExpl);