code: public LogWithPatternAndLevel get(String pattern, Level level) {
          return get(pattern).get(level);
      }
docs: @return a LogWithPatternAndLevel object for the supplied @param message and
  @param level .  This can be cached and reused by callers in performance-sensitive
  cases to avoid performing two ConcurrentHashMap lookups.
  
  Note that the string is the sole key used, so the same string cannot be reused with differing period
  settings; any periods which differ from the first one used are ignored.
  
  @throws IllegalStateException if we exceed the limit on number of RateLimitedLogWithPattern objects
  in any one period; if this happens, it's probable that an already-interpolated string is
  accidentally being used as a log pattern.