docs: def to_oncotator(self):
          """Returns mutation in oncotator input format. Assumes mutations have
          vcf/mpileup style positions."""
          if self.type == ".":
              ref = self.ref
              alt = self.change
              start = self.pos
              end = self.pos
          elif self.type == "-":
              ref = self.change
              alt = "-"
              start = self.pos + 1
              end = start + len(self.change)
          elif self.type == "+":
              ref = "-"
              alt = self.change
              start = self.pos
              end = start + len(self.change)
          else:
              raise(Exception("Unexpected mutation type: {}".format(self.type)))
          return "{chrom}\t{start}\t{end}\t{ref}\t{alt}".format(chrom=self.chrom, start=start,
                                                              end=end, ref=ref, alt=alt)