def indexVariants(variants):
    index = ncl.NCL()

    for start, end, reference, action, has_wildtype, variantseqs in variants:
        index.add(start, end, (reference, action, has_wildtype, variantseqs))

    return index
build index of variants for ranged retrieval.
dataset/ETHPy150Open CGATOxford/cgat/CGAT/Variants.py/indexVariants