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

def add(self, hostname, keytype, key):
        """
        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
        """
        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))