def add_child(self, child):
child_id = getattr(child, '<STR_LIT:id>', None)<EOL>if child_id:<EOL><INDENT>if not hasattr(self, '<STR_LIT>'):<EOL><INDENT>self.children = {}<EOL><DEDENT>if child_id not in self.children:<EOL><INDENT>self.children[child_id] = child<EOL><DEDENT><DEDENT>
Children are GFFFeatures and are defined when added. This is done to avoid memory overheads
        that may be incurred by GFF files that have millions of rows.