docs: private Result execute(ResultType cmdType) throws SparqlException {
      String mimeType = contentType;
      
      // Validate the user-supplied MIME type.
      if (mimeType != null && !ResultFactory.supports(mimeType, cmdType)) {
        logger.warn("Requested MIME content type '{}' does not support expected response type: {}", mimeType, cmdType);
        mimeType = null;
      }
      
      // Get the default MIME type to request
      if (mimeType == null) {
        mimeType = ResultFactory.getDefaultMediaType(cmdType);
      }
      
      if (logger.isDebugEnabled()) {
        logRequest(cmdType, mimeType);
      }
      
      try {
        HttpResponse response = SparqlCall.executeRequest(this, mimeType);
        return ResultFactory.getResult(this, response, cmdType);
      } catch (Throwable t) {
        release();
        throw SparqlException.convert("Error creating SPARQL result from server response", t);
      }
    }