code: def add(self, hostname, keytype, key):
          
          for e in self._entries:
              if (hostname in e.hostnames) and (e.key.get_name() == keytype):
                  e.key = key
                  return
          self._entries.append(HostKeyEntry([hostname], key))
docs: Add a host key entry to the table.  Any existing entry for a
          ``(hostname, keytype)`` pair will be replaced.
  
          :param str hostname: the hostname (or IP) to add
          :param str keytype: key type (``"ssh-rsa"`` or ``"ssh-dss"``)
          :param .PKey key: the key to add