Renamed .flatten() -> .flat
Renamed .flatten() -> .flat


Former-commit-id: 0bbba01608a2cb75977c48a73c734224fa7acc16 [formerly 51275f148a8620e46722ab0ccfbb9131635988e2]
Former-commit-id: 17ebfb1f04008e8672603a8fa5de2cf13eb89042
gem/oq-engine,gem/oq-engine,gem/oq-engine,gem/oq-engine,gem/oq-engine