def get_genotype_ids(samples):
    """
    Get the list of genotype ids from the {sample_id : genotype_id} hash
    If the genotype_id is empty then use the sample_id by default
    :param samples: mapping between sample_id and genotype_id
    :type samples: dict
    :return: list of genotype ids
    :rtype: list
    """
    return [samples[key] if samples[key] else key for key in samples]