<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def as_int(self, val: Tuple[str]) -> int: """Transform a "bits" value to an integer."""

        res = 0
        try:
            for b in val:
                res += 1 << self.bit[b]
        except KeyError:
            return None
        return res