code: def pack_lines_generator(self, pack_size):
      lines = []
      group_ids = []
      current_pack_size = 0
  
      lines_generator = self.lines_generator()
      for group_id, line in lines_generator:
          group_ids.append(group_id)
          lines.append(line)
          current_pack_size += 1
          if current_pack_size == pack_size:
              yield group_ids, lines
              lines = []
              group_ids = []
              current_pack_size = 0
      if current_pack_size != 0:
          yield group_ids, lines
  
file_path: catboost/catboost/python-package/catboost/eval/_readers.py
imports: import pandas
  from .utils import series_to_line
label_desc: Use image node_id 4 for calling the _BaseReader obj's underlying member method code with example usage: obj.pack_lines_generator(pack_size) without return types