A concise slug for this feature.

        Unlike the internal representation, which is 0-based half-open, the
        slug is a 1-based closed interval (a la GFF3).

def slug(self):
        """
        A concise slug for this feature.

        Unlike the internal representation, which is 0-based half-open, the
        slug is a 1-based closed interval (a la GFF3).
        """
        return '{:s}@{:s}[{:d}, {:d}]'.format(self.type, self.seqid,
                                              self.start + 1, self.end)