class_docstr: A CheckpointCallback class that handles additional logging and
  model's checkpointing.
docstr: File's path.
docstr_tok: ["File","'s","path","."]
code: def file_path(self) -> str:
      """File's path."""
  
      return self._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 2 for calling the CheckpointCallback obj's underlying member method code with example usage: obj.file_path() and returns: self