code: def __init__(self, sep, group_feature_num):
      self._sep = sep
      self._group_feature_num = group_feature_num
  
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 1 to create a new _BaseReader object from inherited base classes: object with example: obj = _BaseReader(sep, group_feature_num)