constant ds already defined anspress question answers

Hi,

I have a problem with DS. I see this error PHP Warning: Constant DS already defined in /home4/root/website.com/wp-content/plugins/anspress-question-answer/anspress-question-answer.php on line 273

       private function setup_constants() {
			$plugin_dir = wp_normalize_path( plugin_dir_path( __FILE__ ) );

			define( 'DS', DIRECTORY_SEPARATOR );
			define( 'AP_VERSION', $this->_plugin_version );
			define( 'ANSPRESS_DIR', $plugin_dir );
			define( 'ANSPRESS_URL', plugin_dir_url( __FILE__ ) );
			define( 'ANSPRESS_WIDGET_DIR', $plugin_dir . 'widgets/' );
			define( 'ANSPRESS_THEME_DIR', $plugin_dir . 'templates' );
			define( 'ANSPRESS_THEME_URL', ANSPRESS_URL . 'templates' );
			define( 'ANSPRESS_CACHE_DIR', WP_CONTENT_DIR . '/cache/anspress' );
			define( 'ANSPRESS_CACHE_TIME', HOUR_IN_SECONDS );
			define( 'ANSPRESS_ADDONS_DIR', $plugin_dir . 'addons' );
		}

On line 273 is this define( ‘DS’, DIRECTORY_SEPARATOR );

How to fix this please?

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