https://solr.apache.org/docs/10_0_0/core/org/apache/solr/search/grouping/endresulttransformer/MainEndResultTransformer.html
MainEndResultTransformer (Solr 10.0.0 core API)
declaration: package: org.apache.solr.search.grouping.endresulttransformer, class: MainEndResultTransformer
solrcoreapi