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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 compute_checksum(self):
 """ Calculates checksums for a given file. """

        if self._filename.startswith("s3://"):
            print("Warning: Did not perform client-side checksumming for file in S3. To be implemented.")
            pass
        else:
            checksumCalculator = self.ChecksumCalculator(self._filename)
            self._checksums = checksumCalculator.compute()