docs: def get_alt_lengths(self):
          """Returns the longest length of the variant. For deletions, return is negative,
          SNPs return 0, and insertions are +. None return corresponds to no variant in interval
          for specified individual
  
          """
          #this is a hack to store the # of individuals without having to actually store it
          out = []
          for i in six.moves.range(len(self.genotype)):
              valid_alt = self.get_alt_length(individual=i)
              if not valid_alt:
                  out.append(None)
              else:
                  out.append(max(valid_alt)-len(self.ref))
          return out