use https://github.com/nunocoracao/blowfish.git

themes/blowfish/assets/lib/mermaid/preprocess.d.ts

@@ -0,0 +1,10 @@
+import type { DiagramMetadata } from './diagram-api/types.js';
+/**
+ * Preprocess the given code by cleaning it up, extracting front matter and directives,
+ * cleaning and merging configuration, and removing comments.
+ * @param code - The code to preprocess.
+ * @returns The object containing the preprocessed code, title, and configuration.
+ */
+export declare function preprocessDiagram(code: string): DiagramMetadata & {
+    code: string;
+};