How to access max_score from function score logic?

[Dhiwakar_Kusuma]

Is there a way to access max_score ... I'm trying to do something like below.

GET my_index/_search
{
"query": {
"function_score": {
.....
}
},
"script_score": {
"script": {
"lang": "expression",
"source": "_score / max_score * 20"
}
}
}
}
}