Equivalent functionality of old graphql-tools transformSchema for cloning an executable schema?

[threehams]

I'm working on improving performance for Jest tests, and the most expensive part of each one by far, at about 100-200ms:

const schema = makeExecutableSchema({ typeDefs: schemaStr });
addMockFunctionsToSchema({ schema, mocks, preserveResolvers: true });

(we're out of date on some packages, so addMockFunctions would be the equivalent with latest.)

Since the executable schema doesn't change at all for the whole test, I'd like to run this once, cache the result, and then clone the cached version each time before adding mocks, since addMock functions mutate the existing class. There's a function called transformSchema from graphql-tools which works really well for this:

transformSchema(cachedSchema, []);

However, there doesn't seem to be an equivalent anywhere in the @graphql-tools/ packages.

Is there a function in one of the newer packages that could do this? Or, is there maybe a different solution here?