<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def run_command(self, command, arg=None, is_eval=False, member_id=None):
 """run command on replica set if member_id is specified command will be execute on this server if member_id is not specified command will be execute on the primary Args: command - command string arg - command argument is_eval - if True execute command as eval member_id - member id return command's result """

        logger.debug("run_command({command}, {arg}, {is_eval}, {member_id})".format(**locals()))
        mode = is_eval and 'eval' or 'command'
        hostname = None
        if isinstance(member_id, int):
            hostname = self.member_id_to_host(member_id)
        result = getattr(self.connection(hostname=hostname).admin, mode)(command, arg)
        logger.debug("command result: {result}".format(result=result))
        return result