This DEV-only field was added in 836331ba5f69f2cc53b273ec073fae116db14302 by @sebmarkbage but it's not being used anymore to my knowledge.
import {
  resolveLazyComponentTag,
  createFiberFromTypeAndProps,
  createFiberFromFragment,
  createFiberFromOffscreen,
  createWorkInProgress,
  isSimpleFunctionComponent,
} from './ReactFiber.new';
import {
  retryDehydratedSuspenseBoundary,
  scheduleUpdateOnFiber,
  renderDidSuspendDelayIfPossible,
  markSkippedUpdateLanes,
  getWorkInProgressRoot,
  pushRenderLanes,
  getExecutionContext,
  RetryAfterError,
  NoContext,
} from './ReactFiberWorkLoop.new';
import {setWorkInProgressVersion} from './ReactMutableSource.new';
import {
  requestCacheFromPool,
  pushCacheProvider,
  pushRootCachePool,
  CacheContext,
  getSuspendedCachePool,
  restoreSpawnedCachePool,
  getOffscreenDeferredCachePool,
} from './ReactFiberCacheComponent.new';
import is from 'shared/objectIs';