class_docstr: A CheckpointCallback class that handles additional logging and
  model's checkpointing.
code: def file_path(self, file_path: str) -> None:
      if not isinstance(file_path, str):
          raise e.TypeError("`file_path` should be a string")
  
      self._file_path = file_path
  
imports: from typing import List, TypeVar, Union
  import numpy
  import opytimizer.utils.exception
  from opytimizer.core.space import Space
label_desc: Use image node_id 3 for calling the CheckpointCallback obj's underlying member method code with example usage: obj.file_path(file_path) without return types