Iterate over all issues and count the number of times each callable
        is seen.

def _compute_callables_count(self, iters: Dict[str, Any]):
        """Iterate over all issues and count the number of times each callable
        is seen."""
        count = dict.fromkeys([issue["callable"] for issue in iters["issues"]], 0)
        for issue in iters["issues"]:
            count[issue["callable"]] += 1

        return count