Create another VariantSequence with more supporting reads.

def add_reads(self, reads):
        """
        Create another VariantSequence with more supporting reads.
        """
        if len(reads) == 0:
            return self
        new_reads = self.reads.union(reads)
        if len(new_reads) > len(self.reads):
            return VariantSequence(
                prefix=self.prefix,
                alt=self.alt,
                suffix=self.suffix,
                reads=new_reads)
        else:
            return self