code: def check(self, hostname, key):
          
          k = self.lookup(hostname)
          if k is None:
              return False
          host_key = k.get(key.get_name(), None)
          if host_key is None:
              return False
          return str(host_key) == str(key)
docs: Return True if the given key is associated with the given hostname
          in this dictionary.
  
          @param hostname: hostname (or IP) of the SSH server
          @type hostname: str
          @param key: the key to check
          @type key: L{PKey}
          @return: C{True} if the key is associated with the hostname; C{False}
              if not
          @rtype: bool