cache_add example

sprintf(
                        /* translators: %s: Theme directory name. */
                        __( 'The theme directory "%s" does not exist.' ),
                        esc_html( $this->stylesheet )
                    )
                );
            } else {
                $this->errors = new WP_Error( 'theme_no_stylesheet', __( 'Stylesheet is missing.' ) );
            }
            $this->template    = $this->stylesheet;
            $this->block_theme = false;
            $this->cache_add(
                'theme',
                array(
                    'block_theme' => $this->block_theme,
                    'headers'     => $this->headers,
                    'errors'      => $this->errors,
                    'stylesheet'  => $this->stylesheet,
                    'template'    => $this->template,
                )
            );
            if ( ! file_exists( $this->theme_root ) ) { // Don't cache this one.                 $this->errors->add( 'theme_root_missing', __( '<strong>Error:</strong> The themes directory is either empty or does not exist. Please check your installation.' ) );
            }