code: def lines_generator(self):
      raise NotImplementedError(
          "The base class don't have any lines_reader"
      )
  
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 3 for calling the _BaseReader obj's underlying member method code with example usage: obj.lines_generator() without return types