code: def add_object(self, file_path, file_object, error_fct=None):
          
          error_fct = error_fct or self.raise_os_error
          if not file_path:
              target_directory = self.root
          else:
              target_directory = self.resolve(file_path)
              if not S_ISDIR(target_directory.st_mode):
                  error = errno.ENOENT if self.is_windows_fs else errno.ENOTDIR
                  error_fct(error, file_path)
          target_directory.add_entry(file_object)
docs: Add a fake file or directory into the filesystem at file_path.
  
          Args:
              file_path: The path to the file to be added relative to self.
              file_object: File or directory to add.
              error_class: The error class to be thrown if file_path does
                  not correspond to a directory (used internally(
  
          Raises:
              IOError or OSError: if file_path does not correspond to a
                  directory.