LowPriority: number,
  IdlePriority: number,
  NoPriority: number,
|};
type ReactTypeOfSideEffectType = {|
  NoFlags: number,
  PerformedWork: number,
  Placement: number,
  Incomplete: number,
|};
function getFiberFlags(fiber: Fiber): number {
  
  return fiber.flags !== undefined ? fiber.flags : (fiber: any).effectTag;
}
const getCurrentTime =
  typeof performance === 'object' && typeof performance.now === 'function'
    ? () => performance.now()
    : () => Date.now();
export function getInternalReactConstants(
  version: string,
): {|
  getDisplayNameForFiber: getDisplayNameForFiberType,
  getTypeSymbol: getTypeSymbolType,
  ReactPriorityLevels: ReactPriorityLevelsType,
  ReactTypeOfSideEffect: ReactTypeOfSideEffectType,
  ReactTypeOfWork: WorkTagMap,
|} {
  const ReactTypeOfSideEffect: ReactTypeOfSideEffectType = {
    NoFlags: 0b00,
    PerformedWork: 0b01,