
  [;1m-spec system_monitor(Arg) -> MonSettings[0m
  [;1m                        when[0m
  [;1m                            Arg :: undefined | {MonitorPid, Options},[0m
  [;1m                            MonSettings ::[0m
  [;1m                                undefined | {MonitorPid, Options},[0m
  [;1m                            MonitorPid :: pid(),[0m
  [;1m                            Options :: [system_monitor_option()].[0m

  When called with argument [;;4mundefined[0m, all system performance
  monitoring settings are cleared.

  Calling the function with [;;4m{MonitorPid, Options}[0m as argument is
  the same as calling [;;4merlang:system_monitor(MonitorPid, Options)[0m.

  Returns the previous system monitor settings just like [;;4m[0m
  [;;4merlang:system_monitor/0[0m.
