Where does information come from in opencart?

Question

opencart

These lines write to the variable mail

$data['mail'] = $this->config->get('config_email');
foreach((array)$this->config->get('config_location') as $location_id) {
      $location_info = $this->model_localisation_location->getLocation($location_id);

      if ($location_info) {
        if ($location_info['image']) {
          $image = $this->model_tool_image->resize($location_info['image'], $this->config->get($this->config->get('config_theme') . '_image_location_width'), $this->config->get($this->config->get('config_theme') . '_image_location_height'));
        } else {
          $image = false;
        }

        $data['locations'][] = array(
          'mail'  	    => $location_info['email']
        );
      }
    }

.
How to see the full list of what can be written to variables?