code: public function init_options() {
          if (!is_array($this->options)) {
              $this->options = array();
          }
  
          $options_id = $this->get_id('-options');
          $options = get_option($options_id);
          $need_update = false;
  
          if($options === false) {
              $need_update = true;
              $options = array();
          }
  
          foreach($this->options as $key => $value) {
              if(!array_key_exists($key, $options)) {
                  $options[$key] = $value;
              }
          }
  
          if(!array_key_exists('latest_used_version', $options)) {
              $options['latest_used_version'] = $this->version;
              $need_update = true;
          }
  
          if($need_update === true) {
              update_option($options_id, $options);
          }
  
          return $options;
      }
docs: Initialize plugin's options
  
  @since 0.1.1
  @return array