def fetch_ensembl_exons(build='37'):
    """Fetch the ensembl genes
    
    Args:
        build(str): ['37', '38']
    """
    LOG.info("Fetching ensembl exons build %s ...", build)
    if build == '37':
        url = 'http://grch37.ensembl.org'
    else:
        url = 'http://www.ensembl.org'
    
    dataset_name = 'hsapiens_gene_ensembl'
    
    dataset = pybiomart.Dataset(name=dataset_name, host=url)
    
    attributes = [
        'chromosome_name',
        'ensembl_gene_id',
        'ensembl_transcript_id',
        'ensembl_exon_id',
        'exon_chrom_start',
        'exon_chrom_end',
        '5_utr_start',
        '5_utr_end',
        '3_utr_start',
        '3_utr_end',
        'strand',
        'rank'
    ]
    
    filters = {
        'chromosome_name': CHROMOSOMES,
    }
    
    result = dataset.query(
        attributes = attributes,
        filters = filters
    )
    
    return result
Fetch the ensembl genes
    
    Args:
        build(str): ['37', '38']