tokens: To traverse the returned parse tree you want to look at the Sub field of the returned struct which lists all the subexpressions ( a slice of pointers to syntax.Regexp structs ) .
ner_tags: O O O O O B-Data_Structure O O O O O O B-Variable O O O O B-Data_Structure O O O O O O O O O B-Data_Type O B-Variable B-Data_Structure O O