docs: def filter_against_normal(self, normal_mutations, maf_min=0.2,
                                maf_count_threshold=20, count_min=1):
          """Filters mutations that are in the given normal"""
          assert(normal_mutations.chrom == self.chrom)
          assert(normal_mutations.pos == self.pos)
          assert(normal_mutations.ref == self.ref)
  
          def passes_normal_criteria(mut):
              return (mut.count >= maf_count_threshold and mut.maf > maf_min) or \
                  (mut.count < maf_count_threshold and mut.count > count_min)
  
          nms = normal_mutations
          muts = MutationsAtSinglePosition(self.chrom, self.pos, self.cov, self.ref)
  
          for snv in self.snvs:
              if not (snv in nms.snvs and passes_normal_criteria(nms.snvs[snv])):
                  muts.add_snv(self.snvs[snv])
  
          for dlt in self.deletions:
              if not (dlt in nms.deletions and passes_normal_criteria(nms.deletions[dlt])):
                  muts.add_deletion(self.deletions[dlt])
  
          for ins in self.insertions:
              if not (ins in nms.insertions and passes_normal_criteria(nms.insertions[ins])):
                  muts.add_insertion(self.insertions[ins])
  
          return muts