private function addCustomVariables(Model $model, $numberOfVarsToAdd, OutputInterface $output)
{
for ($index = 0; $index < $numberOfVarsToAdd; $index++) {
$indexAdded = $model->addCustomVariable();
$this->progress->advance();
$output->writeln(' <info>Added a variable in scope "' . $model->getScopeName() . '" having the index ' . $indexAdded . '</info>');
}
}