string formatting supports implicit `str`ifying. However, string format specifiers don't appear to be compatible with this, only explicit `str` objects (regardless of using type=`s`). I cannot find this behavior documented anywhere without pulling up the cpython code. default ubuntu 20.04 python3.8 install. using an explicit `str()` call is workable but it's not very clean especially in my use case where it now liters the code.

```
obj = object()
explicit = str(obj)
print(f"{explicit:.5}")
print(f"{obj}")
print(f"{obj:.5}") # TypeError: unsupported format string passed to object.__format__

```

Question:

* Have I interpreted this correctly
* where should I be looking to glean this info myself (if exists outside cpython code), and
* is there any way accomplish format specifiers `{:...}` while relying on the implicit `str()`ification?