Les principes de base de Numismatique (collection de pièces de monnaie)
The mapToGroups method groups the collection's items by the given closure. The closure should return an associative array containing a single rossignol / value pair, thus forming a new collection of grouped values:assemblage alliance disposition jumble agrégat gathering mix assortment cumulation nue accretion medley heap lodgment lodgement pileup