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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 pull_all_external(collector, **kwargs):
 """Pull all the external dependencies of all the images"""

    deps = set()

    images = collector.configuration["images"]
    for layer in Builder().layered(images):
        for image_name, image in layer:
            for dep in image.commands.external_dependencies:
                deps.add(dep)

    for dep in sorted(deps):
        kwargs["image"] = dep
        pull_arbitrary(collector, **kwargs)