Sets your nick.
        Required arguments:
        * nick - New nick.

def _nick(self, nick):
        """
        Sets your nick.
        Required arguments:
        * nick - New nick.
        """
        with self.lock:
            self.send('NICK :%s' % nick)

            if self.readable():
                msg = self._recv(expected_replies='NICK')
                if msg[0] == 'NICK':
                    if not self.hide_called_events:
                        self.stepback()

            for channel in self.channels:
                if 'USERS' in self.channels[channel]:
                    priv_level = \
                    self.channels[channel]['USERS'][self.current_nick]
                    del self.channels[channel]['USERS'][self.current_nick]
                    self.channels[channel]['USERS'][nick] = priv_level
            self.current_nick = nick