code: def to_str(self, obj):
      return "".join(str(obj).split())
  
file_path: qlib/tests/data_mid_layer_tests/test_handler.py
imports: import os
  import pickle
  import shutil
  import unittest
  from qlib.tests import TestAutoData
  from qlib.data import D
  from qlib.data.dataset.handler import DataHandlerLP
label_desc: Use image node_id 1 for calling the HandlerTests obj's underlying member method code with example usage: obj.to_str(obj) and returns: str