System.debug(logginglevel.WARN, 'some text');

global class xt {
    global static void log(String message){
        System.debug(logginglevel.WARN , message);
    }
}

epx.xt.log('123');

40.0 APEX_CODE,WARN;APEX_PROFILING,WARN;CALLOUT,WARN;DB,WARN;SYSTEM,WARN
Execute Anonymous: epx.xt.log('123');
19:44:10.186 (186571682)|USER_INFO|[EXTERNAL]|0051i000000OJCw|heim@xe372.elastify.eu|Mitteleuropäische Normalzeit|GMT+02:00
19:44:10.186 (186624077)|EXECUTION_STARTED
19:44:10.186 (186635584)|CODE_UNIT_STARTED|[EXTERNAL]|execute_anonymous_apex
19:44:10.186 (197050273)|CODE_UNIT_FINISHED|execute_anonymous_apex
19:44:10.186 (198123764)|EXECUTION_FINISHED

START APEX EXECUTION
40.0 APEX_CODE,WARN;APEX_PROFILING,WARN;CALLOUT,WARN;DB,WARN;SYSTEM,WARN
20:07:26.294 (294745247)|USER_INFO|[EXTERNAL]|0050Y000001DPSm|heim@xe100.elastify.eu|Mitteleuropäische Normalzeit|GMT+02:00
20:07:26.294 (294786251)|EXECUTION_STARTED
20:07:26.294 (294797532)|CODE_UNIT_STARTED|[EXTERNAL]|execute_anonymous_apex
20:07:26.294 (322596175)|USER_DEBUG|[459]|WARN|123
20:07:26.294 (322725058)|CODE_UNIT_FINISHED|execute_anonymous_apex
20:07:26.294 (324152760)|EXECUTION_FINISHED

START APEX EXECUTION
40.0 APEX_CODE,WARN;APEX_PROFILING,WARN;CALLOUT,WARN;DB,WARN;SYSTEM,WARN
19:48:16.217 (217950018)|USER_INFO|[EXTERNAL]|0051i000000OJCw|heim@xe372.elastify.eu|Mitteleuropäische Normalzeit|GMT+02:00
19:48:16.217 (218000232)|EXECUTION_STARTED
19:48:16.217 (218008004)|CODE_UNIT_STARTED|[EXTERNAL]|execute_anonymous_apex
19:48:16.217 (227248124)|ENTERING_MANAGED_PKG|epx
19:48:16.217 (228472125)|ENTERING_MANAGED_PKG|epx
19:48:16.217 (228890734)|ENTERING_MANAGED_PKG|epx
19:48:16.217 (229007596)|ENTERING_MANAGED_PKG|epx
19:48:16.217 (229554806)|ENTERING_MANAGED_PKG|epx
19:48:16.217 (229915053)|CODE_UNIT_FINISHED|execute_anonymous_apex
19:48:16.217 (231001697)|EXECUTION_FINISHED