Thanks for the suggestion but I'm going to decline.

* The need for this is very low.  

* It's easy to roll your own.

* The code for `count('', 'a')` and `count((), (1,))` isn't intelligible.

* Without special casing, the code for `count('', 'a')` and `count((), (1,))` is highly inefficient.  We advise people not to use the 's = s + t' pattern in a loop for sequences because it leads to quadratic behavior.