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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 current(self):
 """ Display the current database revision """


        config = self.alembic_config()
        script = ScriptDirectory.from_config(config)

        revision = 'base'

        def display_version(rev, context):
            for rev in script.get_all_current(rev):
                nonlocal revision
                revision = rev.cmd_format(False)

            return []

        with EnvironmentContext(config, script, fn=display_version):
            script.run_env()

        return revision