protoBuilder.setTimeLimit(task.getTimeLimit());
protoBuilder.setMemoryLimit(task.getMemoryLimit());
protoBuilder.setOutputLimit(task.getOutputLimit());
protoBuilder.setTestsCount(task.getNumberOfTests());
Grade gradeProto = protoBuilder.build();
DataOutputStream dataOutput = new DataOutputStream(os);
dataOutput.writeInt(gradeProto.getSerializedSize());
gradeProto.writeTo(dataOutput);
// we will continue work with os, so do not close dataOutput.
}