syntax_data: {"ast_node_type":"other","tokens":[{"end":98,"kind":"keyword","start":0,"text":"///"}]}
source_snippet:     /// the slice for the beginning of the span and an index in the slice for the end of the span.
context_before:     /// extract function takes three arguments: a string slice containing the source, an index in
context_after:     pub fn span_to_source<F, T>(&self, sp: Span, extract_source: F) -> Result<T, SpanSnippetError>