syntax_data: {"ast_node_type":"other","tokens":[{"end":61,"kind":"keyword","start":0,"text":"for"}]}
source_snippet:         for (&head, &path_from_entry) in heads.heads.iter() {
context_before:     fn merge(&mut self, heads: &CycleHeads) {
context_after:             self.insert(head, path_from_entry);