public function get_files( $variable_price_id = null ) {
    if( ! isset( $this->files ) ) {

      $this->files = array();

      // Bundled products are not allowed to have files
      if( $this->is_bundled_download() ) {
        return $this->files;
      }

      $download_files = get_post_meta( $this->ID, 'edd_download_files', true );

      if ( $download_files ) {


        if ( ! is_null( $variable_price_id ) && $this->has_variable_prices() ) {

          foreach ( $download_files as $key => $file_info ) {

            if ( isset( $file_info['condition'] ) ) {

              if ( $file_info['condition'] == $variable_price_id || 'all' === $file_info['condition'] ) {

                $this->files[ $key ] = $file_info;

              }

            }

          }

        } else {

          $this->files = $download_files;

        }

      }

    }

    return apply_filters( 'edd_download_files', $this->files, $this->ID, $variable_price_id );

  }