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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 default_hub(hub_name, genome, email, short_label=None, long_label=None):
 """ Returns a fully-connected set of hub components using default filenames. Parameters hub_name : str Name of the hub genome : str Assembly name (hg38, dm6, etc) email : str Email to include with hub. short_label : str Short label for the hub. If None, defaults to the value of `hub_name` long_label : str Long label for the hub. If None, defaults to the value of `short_label`. """

    if short_label is None:
        short_label = hub_name
    if long_label is None:
        long_label = short_label

    hub = Hub(
        hub=hub_name,
        short_label=short_label,
        long_label=long_label,
        email=email)

    genome = Genome(genome)
    genomes_file = GenomesFile()
    trackdb = TrackDb()
    hub.add_genomes_file(genomes_file)
    genomes_file.add_genome(genome)
    genome.add_trackdb(trackdb)
    return hub, genomes_file, genome, trackdb