code: def _get_ref_alt(self, var, boundary):
          
  
          # Get reference allele
          if var.posedit.edit.type == "ins" or var.posedit.edit.type == "dup":
              ref = ""
          else:
              # For NARefAlt and Inv
              if var.posedit.edit.ref_s is None or var.posedit.edit.ref == "":
                  ref = self._fetch_bounded_seq(var, var.posedit.pos.start.base - 1,
                                                var.posedit.pos.end.base, 0, boundary)
              else:
                  ref = var.posedit.edit.ref
  
          # Get alternative allele
          if var.posedit.edit.type == "sub" or var.posedit.edit.type == "delins" or var.posedit.edit.type == "ins":
              alt = var.posedit.edit.alt
          elif var.posedit.edit.type == "del":
              alt = ""
          elif var.posedit.edit.type == "dup":
              alt = var.posedit.edit.ref or self._fetch_bounded_seq(
                  var, var.posedit.pos.start.base - 1, var.posedit.pos.end.base, 0, boundary)
          elif var.posedit.edit.type == "inv":
              alt = reverse_complement(ref)
          elif var.posedit.edit.type == "identity":
              alt = ref
  
          return ref, alt
docs: Get reference allele and alternative allele of the variant