code: public String getCauseStackTraceAsString(final List<String> packages, final String suffix) {
          return getCauseStackTraceAsString(packages, PlainTextRenderer.getInstance(), suffix);
      }
docs: Formats the Throwable that is the cause of this Throwable.
  
  @param packages The List of packages to be suppressed from the trace.
  @param suffix
  @return The formatted Throwable that caused this Throwable.