code: def reads_supporting_variants(variants, samfile, **kwargs):
      
      for variant, allele_reads in reads_overlapping_variants(
              variants=variants,
              samfile=samfile,
              **kwargs):
          yield variant, filter_non_alt_reads_for_variant(variant, allele_reads)
docs: Given a SAM/BAM file and a collection of variants, generates a sequence
      of variants paired with reads which support each variant.