Returns start position of first flank sequence, plus a list of sequences -
        the REF, plus one for each ALT.sequence. Order same as in ALT column

def inferred_var_seqs_plus_flanks(self, ref_seq, flank_length):
        '''Returns start position of first flank sequence, plus a list of sequences -
        the REF, plus one for each ALT.sequence. Order same as in ALT column'''
        flank_start = max(0, self.POS - flank_length)
        flank_end = min(len(ref_seq) - 1, self.ref_end_pos() + flank_length)
        seqs = [ref_seq[flank_start:self.POS] + self.REF + ref_seq[self.ref_end_pos() + 1: flank_end + 1]]

        for alt in self.ALT:
            seqs.append(ref_seq[flank_start:self.POS] + alt + ref_seq[self.ref_end_pos() + 1: flank_end + 1])

        return flank_start, seqs