A string specifying an entity prototype flag.
"not-rotatable" | "placeable-neutral" | "placeable-player" | "placeable-enemy" | "placeable-off-grid" | "player-creation" | "building-direction-8-way" | "filter-directions" | "get-by-unit-number" | "breaths-air" | "not-repairable" | "not-on-map" | "not-deconstructable" | "not-blueprintable" | "hide-alt-info" | "not-flammable" | "no-automated-item-removal" | "no-automated-item-insertion" | "no-copy-paste" | "not-selectable-in-game" | "not-upgradable" | "not-in-kill-statistics" | "building-direction-16-way" | "snap-to-rail-support-spot" | "not-in-made-in"