I want to know the answer to the following question:
How may state prisoners seek to have a death sentence overturned in federal court?
All the background I'm provided with is that "Federal habeas corpus is a species of collateral review, and it is the only way that state prisoners may attack a death sentence in federal court (other than petitions for certiorari to the United States Supreme Court after both direct review and state collateral review).". Is that enough to answer the question?