custom code for superRefine

[luisrudge]

z.string()
  .email()
  .superRefine(async (email, ctx) => {
    ctx.addIssue({ code: "my-error-code" });
  });

Doc says:

Normally refinements always create issues with a ZodIssueCode.custom error code, but with superRefine you can create any issue of any code. Each issue code is described in detail in the Error Handling guide: ERROR_HANDLING.md.

My understanding is that I can create any custom code I want. Is that understanding correct or does it mean that I can use any of the pre-existing codes only?