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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 build_region_list(service, chosen_regions = [], partition_name = 'aws'):
 """ Build the list of target region names :param service: :param chosen_regions: :param partition_name: :return: """

    service = 'ec2containerservice' if service == 'ecs' else service # Of course things aren't that easy...
    # Get list of regions from botocore
    regions = Session().get_available_regions(service, partition_name = partition_name)
    if len(chosen_regions):
        return list((Counter(regions) & Counter(chosen_regions)).elements())
    else:
        return regions