How scorePayload is used as a Scoring Factor?

[Furkan KAMACI]

Hi;

At TFIDFSimilarity class documentaton says that about return value of
scorePayload():

*An implementation dependent float to be used as a scoring factor*

However when I read here:
http://lucene.apache.org/core/4_6_0/core/org/apache/lucene/search/similarities/TFIDFSimilarity.html

I don't see a coefficient as like payload. Where and how it is used?

Thanks;
Furkan KAMACI