protected function mergeWithExisting($entitiesByModule)
    {
        // For each module do a simple merge of the default yml with these strings
        foreach ($entitiesByModule as $module => $messages) {
            // Load existing localisations
            $masterFile = "{$this->basePath}/{$module}/lang/{$this->defaultLocale}.yml";
            $existingMessages = $this->getReader()->read($this->defaultLocale, $masterFile);

            // Merge
            if ($existingMessages) {
                $entitiesByModule[$module] = array_merge(
                    $existingMessages,
                    $messages
                );
            }
        }
        return $entitiesByModule;
    }