<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def _decode_data(self, data):
 """`data` is array.array"""

        self.major = data[0]

        if data[1] is 0xff:
            self.minor = data[1]
        elif data[1] <= 0x99:
            self.minor = int(data[1:2].tostring().decode('bcd+'))
        else:
            raise DecodingError()