code: public void setMetatags(Map<String, String> metatags, String key) {
          if (metatags != null) {
              TSDBEntity.validateTags(metatags);
              _metatags.clear();
              _metatags.putAll(metatags);
              _key = key;
          }
      }
docs: Replaces the metatags for a metric. Metatags cannot use any of the reserved tag names.
  
  
  @param  metatags   A key-value pairs of metatags. Cannot be null or empty.
  @param  key        A unique identifier to be used while indexing this metatags into a schema db.