def get_flanks(snp_region, flank_size):
    """return the flanking regions for a location in a chromosome"""
    region_seqs = snp_region.seq
    rawflank5 = region_seqs[0: flank_size]
    rawflank3 = region_seqs[flank_size+1: flank_size*2+1]
    ensembl_ref = region_seqs[flank_size: flank_size+1]
    return rawflank5, ensembl_ref, rawflank3