@property<EOL><INDENT>def slug(self):<DEDENT>
return '<STR_LIT>'.format(self.type, self.seqid,<EOL>self.start + <NUM_LIT:1>, self.end)<EOL>
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).