<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 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