code: protected final String baseToRules(boolean escapeUnprintable) {
          // The base class implementation of toRules munges the ID into
          // the correct format.  That is: foo => ::foo
          // KEEP in sync with rbt_pars
          if (escapeUnprintable) {
              StringBuffer rulesSource = new StringBuffer();
              String id = getID();
              for (int i=0; i<id.length();) {
                  int c = UTF16.charAt(id, i);
                  if (!Utility.escapeUnprintable(rulesSource, c)) {
                      UTF16.append(rulesSource, c);
                  }
                  i += UTF16.getCharCount(c);
              }
              rulesSource.insert(0, "::");
              rulesSource.append(ID_DELIM);
              return rulesSource.toString();
          }
          return "::" + getID() + ID_DELIM;
      }
docs: Returns a rule string for this transliterator.  This is
  a non-overrideable base class implementation that subclasses
  may call.  It simply munges the ID into the correct format,
  that is, "foo" =&gt; "::foo".
  @param escapeUnprintable if true, then unprintable characters
  will be converted to escape form backslash-'u' or
  backslash-'U'.