tokens: You can also use Adjacency List , now go ahead and google it to have some understanding of how to use Adjacency Matrices and Adjacency Lists , and come back with some real problem then .
ner_tags: O O O O O B-Data_Structure O O O O O O O O O O O O O O O O B-Data_Structure O O B-Data_Structure O O O O O O O O O O