bug: missing IDE autocomplete for passthrough methods.

**Describe the bug**
IDE autocompletion does not work for passthrough methods.

**To Reproduce**
Install the SDK and attempt to get autocompletes in any IDE for `MemoryClient`.

**Expected behavior**
proper auto completes.

**Additional Context**
This is because the passthrough methods leverage python `__getattr__` to directly proxy to the boto client. The static analysis done by IDEs is not able to pick this up, resulting in missing autocompletes.

One potential solution could be to generate `.pyi` and ship them as part of the SDK.