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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 _checksum(self):
 """Performs the checksum for the current TLE."""

        for line in [self._line1, self._line2]:
            check = 0
            for char in line[:-1]:
                if char.isdigit():
                    check += int(char)
                if char == "-":
                    check += 1

            if (check % 10) != int(line[-1]):
                raise ChecksumError(self._platform + " " + line)