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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 cast_to_subclass(self):
 """ Load the bundle file from the database to get the derived bundle class, then return a new bundle built on that class :return: """

        self.import_lib()
        self.load_requirements()

        try:
            self.commit()  # To ensure the rollback() doesn't clear out anything important
            bsf = self.build_source_files.file(File.BSFILE.BUILD)
        except Exception as e:
            self.log('Error trying to create a bundle source file ... {} '.format(e))
            raise
            self.rollback()
            return self

        try:
            clz = bsf.import_bundle()

        except Exception as e:

            raise BundleError('Failed to load bundle code file, skipping : {}'.format(e))

        b = clz(self._dataset, self._library, self._source_url, self._build_url)
        b.limited_run = self.limited_run
        b.capture_exceptions = self.capture_exceptions
        b.multi = self.multi


        return b