docs: public static Tag parseTag(String tagString) {
      String k;
      String v;
      int eqIndex = tagString.indexOf("=");
  
      if (eqIndex < 0) {
        throw new IllegalArgumentException("key and value must be separated by '='");
      }
  
      k = tagString.substring(0, eqIndex).trim();
      v = tagString.substring(eqIndex + 1, tagString.length()).trim();
      return newTag(k, v);
    }