syntax_data: {"ast_node_type":"other","tokens":[{"end":39,"kind":"keyword","start":0,"text":".map(|ref_transition|"}]}
source_snippet:                 .map(|ref_transition| {
context_before:             let ref_transitions = ref_transitions
context_after:                     let a_dst = a_transitions.ref_transitions.get(ref_transition).copied();