syntax_data: {"ast_node_type":"other","tokens":[{"end":53,"kind":"keyword","start":0,"text":"self.heads.first_key_value().map(|(k,"}]}
source_snippet:         self.heads.first_key_value().map(|(k, _)| *k)
context_before:     fn opt_lowest_cycle_head(&self) -> Option<StackDepth> {
context_after:     }