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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 gene_id_of_associated_transcript(effect):
 """ Ensembl gene ID of transcript associated with effect, returns None if effect does not have transcript. """

    return apply_to_transcript_if_exists(
        effect=effect,
        fn=lambda t: t.gene_id,
        default=None)