Incorrect code in guide for persistence

[ConanChenTookMyName]

Describe the bug
In the guide for persistence, the code provided for setting up a custom cache seems to be incorrect.

According to the guide, ClientOptionsType's cache field should expect a function with an "instance" parameter, and that argument should then be passed into a Cache constructor. However, in the actual definition of ClientOptionsType, the cache field expects a function with no parameters.

To Reproduce
Steps to reproduce the behavior:

1. Try the code in the guide for persistence.

Expected behavior
The guide should provide code that demonstrates the correct API usage.

Package:

• Version 7.2.6

Additional context
The unit tests for Cache call a createCache function to set up a Client with a custom cache, but that function is only defined in "cache.utils.ts" under the "tests" folder.