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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 database_current_migration(self):
 """ Return the current migration in the database. """

        # If the table doesn't even exist, return None.
        if not self.migration_table.exists(self.session.bind):
            return None

        # Also return None if self.migration_data is None.
        if self.migration_data is None:
            return None

        return self.migration_data.version