code: def __is_valid_pos(pos_tuple, valid_pos):
      # type: (Tuple[text_type,...],List[Tuple[text_type,...]])->bool
      
      def is_valid_pos(valid_pos_tuple):
          # type: (Tuple[text_type,...])->bool
          length_valid_pos_tuple = len(valid_pos_tuple)
          if valid_pos_tuple == pos_tuple[:length_valid_pos_tuple]:
              return True
          else:
              return False
  
      seq_bool_flags = [is_valid_pos(valid_pos_tuple) for valid_pos_tuple in valid_pos]
  
      if True in set(seq_bool_flags):
          return True
      else:
          return False
docs: This function checks token's pos is with in POS set that user specified.
      If token meets all conditions, Return True; else return False