clear () {
    const removed = {}
    utils.forOwn(this._collections, (collection, name) => {
      removed[name] = collection.removeAll()
      this._completedQueries[name] = {}
    })
    return removed
  }
Remove __all__ records from the in-memory store and reset
{@link SimpleStore#_completedQueries}.

@method SimpleStore#clear
@returns {Object} Object containing all records that were in the store.
@see SimpleStore#remove
@see SimpleStore#removeAll
@since 3.0.0