The verse can be read in two ways. The story assumes that the snake refuses to take back the poison. But there is no negative particle qualifying the verb, so it must be read as a rhetorical question: “I shall take back what I have vomited?” In this reading, they refuse to take it back even “for the sake of life” because they are threatened with death if they refuse. Alternatively, however, the speaker is saying that they have vomited the poison for the sake of life—i.e. that they took a purgative—but nonetheless they shall eat their poisoned vomit even though it means their death. In this reading, the speaker is likely a person rather than a snake, and the “vomit” actual vomit, not emitted poison. The reason why they resort to such drastic measures is not clear, and I fear we have lost the original story that would have made the context meaningful. Nonetheless, I think this interpretation reflects the Pali more directly.