code: private URI _getSpecURI(String spec) {
          URI specURI = URI.create(spec);
  
          if (_scheme.indexOf(':') == -1) {
              return specURI;
          }
          
          String schemeSpecificPart = specURI.getSchemeSpecificPart();
          return URI.create(schemeSpecificPart);
      }
docs: the appropriate URI that can be used to retrieve the needed parts.