protected function get_field( \WP_Post $post ){
        $html = parent::get_field($post);
        return $html.sprintf('<p class="inline-error"><i class="dashicons dashicons-location-alt"></i> %s</p>', $this->__('Can\'t find map point. Try another string'));
    }
protected function get_field( \WP_Post $post ){
        $html = parent::get_field($post);
        return $html.sprintf('<p class="inline-error"><i class="dashicons dashicons-location-alt"></i> %s</p>', $this->__('Can\'t find map point. Try another string'));
    }
protected function get_field ( \ WP_Post $ post ) { $ html = parent :: get_field ( $ post ) ; return $ html . sprintf ( '<p class="inline-error"><i class="dashicons dashicons-location-alt"></i> %s</p>' , $ this -> __ ( 'Can\'t find map point. Try another string' ) ) ; }
Add error message.

@param \WP_Post $post
@return string
Add error message .