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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 create(client, output_file, revision, paths):
 """Create a workflow description for a file."""

    graph = Graph(client)
    outputs = graph.build(paths=paths, revision=revision)

    output_file.write(
        yaml.dump(
            ascwl(
                graph.ascwl(outputs=outputs),
                filter=lambda _, x: x is not None and x != [],
                basedir=os.path.dirname(getattr(output_file, 'name', '.')) or
                '.',
            ),
            default_flow_style=False
        )
    )