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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _construct_mongos(self, logpath, port, configdb):
 """Construct command line strings for a mongos process."""

        extra = ''

        auth_param = ''
        if self.args['auth']:
            key_path = os.path.abspath(os.path.join(self.dir, 'keyfile'))
            auth_param = '--keyFile %s' % key_path

        if self.unknown_args:
            extra = self._filter_valid_arguments(self.unknown_args,
                                                 "mongos") + extra

        extra += ' ' + self._get_ssl_server_args()

        path = self.args['binarypath'] or ''
        if os.name == 'nt':
            newlogpath = logpath.replace('\\', '\\\\')
            command_str = ("start /b %s --logpath \"%s\" --port %i --configdb %s "
                           "%s %s " % (os.path.join(path, 'mongos'),
                                       newlogpath, port, configdb,
                                       auth_param, extra))
        else:
            command_str = ("%s --logpath \"%s\" --port %i --configdb %s %s %s "
                           "--fork" % (os.path.join(path, 'mongos'), logpath,
                                       port, configdb, auth_param, extra))

        # store parameters in startup_info
        self.startup_info[str(port)] = command_str