Violette Le Duc. The Taxi, aka Le Taxi (1971
Because they bring champagne, truffle pâté, and rolls (no basket is mentioned), critics have called this kiddie-porn tryst between a brother and sister a picnic. Therefore, if it is called a picnic (although neither the English word nor the French pique-nique is used), it is a picnic.
See Violette Le Duc. The Taxi, aka Le Taxi (1971). Translated by Helen Weaver (1972)
Featured Image: The jacket design, which resembles a grotesque mask, is by Pat de Groot