docs: def _verifyHostKey(self, hostKey, fingerprint):
          """Called when ssh transport requests us to verify a given host key.
          Return a deferred that callback if we accept the key or errback if we
          decide to reject it.
          """
          if fingerprint in self.knownHosts:
              return defer.succeed(True)
          return defer.fail(UnknownHostKey(hostKey, fingerprint))