tokens: Note that as a more efficient way for accessing to next items and refuse of multiple indexing you can use iter() function to create an iterator object from your list ( from second element to end ) and access to next elements in each iteration with next :
ner_tags: O O O O O O O O O O O O O O O O O O O O B-Function O O O 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-Code_Block O