syntax_data: {"ast_node_type":"other","tokens":[{"end":54,"kind":"keyword","start":0,"text":"left:"}]}
source_snippet:                             left: span.shrink_to_lo(),
context_before:                             start_of_line: sm.span_extend_to_line(span).shrink_to_lo(),
context_after:                             right: span.shrink_to_hi(),