def delete(key)
      deleted = @store.delete(key)
      @on_write_failure.call(key) if !deleted && @on_write_failure
      RecordCache::Base.logger.debug{ "Version Store: deleted #{key}" }
      deleted
    end
def delete(key)
      deleted = @store.delete(key)
      @on_write_failure.call(key) if !deleted && @on_write_failure
      RecordCache::Base.logger.debug{ "Version Store: deleted #{key}" }
      deleted
    end
Delete key from the version store (records cached in the Record Store belonging to this key will become unreachable)