@Override
    public String toString() {
        StringBuilder retVal = new StringBuilder();
        retVal.append("Struct (").append(getDataType()).append("): ");
        int[] increasing = getInOrder();
        for (int id : increasing) {
            retVal.append(getDataType().getField(id)).append("=").append(values.get(id)).append(", ");
        }
        if (increasing.length > 0)
            retVal.setLength(retVal.length() - 2);
        return retVal.toString();
    }
Clears this and assigns from the given {@link StructuredFieldValue}
document/src/main/java/com/yahoo/document/datatypes/Struct.java