Man pages matching name mongoc_collection_estimated_document_count in section 3:

mongoc_collection_estimated_document_count.3.en	debian 10 / libmongoc-doc
mongoc_collection_estimated_document_count.3.en	debian 11 / libmongoc-doc
mongoc_collection_estimated_document_count.3.en	debian 12 / libmongoc-doc