langchain/tools/file_management/utils.py/BaseFileToolMixin/get_relative_path
class BaseFileToolMixin:    def get_relative_path(self, file_path: str) -> Path:
        """Get the relative path, returning an error if unsupported."""
        if self.root_dir is None:
            return Path(file_path)
        return get_validated_relative_path(Path(self.root_dir), file_path)