docs: def CheckHashes(self, hashes):
      """Check hashes against the filestore.
  
      Blobs use the hash in the schema:
      aff4:/files/hash/generic/sha256/[sha256hash]
  
      Args:
        hashes: A list of Hash objects to check.
  
      Yields:
        Tuples of (RDFURN, hash object) that exist in the store.
      """
      hash_map = {}
      for hsh in hashes:
        if hsh.HasField("sha256"):
          # The canonical name of the file is where we store the file hash.
          hash_map[aff4.ROOT_URN.Add("files/hash/generic/sha256").Add(
              str(hsh.sha256))] = hsh
  
      for metadata in aff4.FACTORY.Stat(list(hash_map)):
        yield metadata["urn"], hash_map[metadata["urn"]]