code: public static List<String> getMustacheKeys(final String template) {
          final Set<String> keys = new HashSet<>();
  
          if (StringUtils.isNotEmpty(template)) {
              final Matcher matcher = MUSTACHE_PATTERN.matcher(template);
  
              while(matcher.find()) {
                  keys.add(matcher.group(1));
              }
  
          }
  
          return new ArrayList<>(keys);
      }
docs: Scans given template for mustache keys (syntax {{value}}).
  
  @return empty list if no mustache key is found.