syntax_data: {"ast_node_type":"function","tokens":[{"end":96,"kind":"keyword","start":0,"text":"fn"}]}
source_snippet:     fn extend_from_child(&mut self, this: StackDepth, step_kind: PathKind, child: &CycleHeads) {
context_before:     /// itself.
context_after:         for (&head, &path_from_entry) in child.heads.iter() {