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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _unpack_int_base128(varint, offset):
 """Implement Perl unpack's 'w' option, aka base 128 decoding."""

        res = ord(varint[offset])
        if ord(varint[offset]) >= 0x80:
            offset += 1
            res = ((res - 0x80) << 7) + ord(varint[offset])
            if ord(varint[offset]) >= 0x80:
                offset += 1
                res = ((res - 0x80) << 7) + ord(varint[offset])
                if ord(varint[offset]) >= 0x80:
                    offset += 1
                    res = ((res - 0x80) << 7) + ord(varint[offset])
                    if ord(varint[offset]) >= 0x80:
                        offset += 1
                        res = ((res - 0x80) << 7) + ord(varint[offset])
        return res, offset + 1