code: function (parser, reporter) {
            var rule = this
            parser.addListener('startrule', function (event) {
              var selectors = event.selectors,
                selector,
                part,
                modifier,
                idCount,
                i, j, k
  
              for (i = 0; i < selectors.length; i++) {
                selector = selectors[i]
                idCount = 0
  
                for (j = 0; j < selector.parts.length; j++) {
                  part = selector.parts[j]
                  if (part.type == parser.SELECTOR_PART_TYPE) {
                    for (k = 0; k < part.modifiers.length; k++) {
                      modifier = part.modifiers[k]
                      if (modifier.type == 'id') {
                        var id = modifier.text
                        var ids = reporter.stats['_elements']
                        if (!ids) {
                          ids = []
                          reporter.stat('_elements', ids)
                        }
                        ids.push(modifier)
                      }
                    }
                  }
                }
              }
  
            })
          }
docs: initialization