code: def populateFromFile(self, dataUrls, indexFiles):
          
          assert len(dataUrls) == len(indexFiles)
          for dataUrl, indexFile in zip(dataUrls, indexFiles):
              varFile = pysam.VariantFile(dataUrl, index_filename=indexFile)
              try:
                  self._populateFromVariantFile(varFile, dataUrl, indexFile)
              finally:
                  varFile.close()
docs: Populates this variant set using the specified lists of data
          files and indexes. These must be in the same order, such that
          the jth index file corresponds to the jth data file.