Creating a Log entry using WLST

I am trying to create a Log entry in my domain's config XML with the following
lines. This is not working and I am getting an error saying that the path cannot
be resolved. Can someone tell me how to create the log entry? Do I need a create
line before this? How do I create a logging mbean.

cd("/Servers/AdminServer/Log/AdminServer")
print "Setting attributes for mbean type Log"
set("LogFileSeverity", "Warning")
set("MemoryBufferSeverity", "Trace")
set("Log4jLoggingEnabled", "true")
set("RedirectStdoutToServerLogEnabled", "false")
set("DomainLogBroadcastSeverity", "Warning")
set("StdoutSeverity", "Notice")