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