There isn't and there doesn't need to be, because newspapers should be read as evidence rather than as authority.
Like any publication, the WP is what it is. It has particular staff, history, reputaiton etc, all of which make it strong in some ways but weak in others, including bias. Bezos' ownership of the paper is yet one more layer on all that.
There is, and never was, any alternative to reading stuff with your bullshit detector turned on.
Even if the answer is "no", that doesn't mean we should fall back to assuming WaPo is fully editorially independent. Just as our (current) inability to prove P != NP doesn't mean we should assume P = NP.
