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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 verify(opts):
 """ Verify that one or more resources were downloaded successfully. """

    resources = _load(opts.resources, opts.output_dir)
    if opts.all:
        opts.resource_names = ALL
    invalid = _invalid(resources, opts.resource_names)
    if not invalid:
        if not opts.quiet:
            print("All resources successfully downloaded")
        return 0
    else:
        if not opts.quiet:
            print("Invalid or missing resources: {}".format(', '.join(invalid)))
        return 1