code: def _inner_send(self, message):
      if self.out_file is None:
          if not os.path.exists(command_path):
              os.makedirs(command_path, exist_ok=True)
  
          if self.node_id is None:
              file_name = os.path.join(
                  command_path,
                  "%s.txt" % runner_commands_file_name_prefix,
              )
          else:
              file_name = os.path.join(
                  command_path,
                  "%s_%s.txt"
                  % (runner_commands_file_name_prefix, self.node_id),
              )
          self.out_file = open(file_name, "ab")
  
      self.out_file.write(message)
      self.out_file.write(b"\n")
      self.out_file.flush()
  
file_path: nni/nni/tools/trial_tool/file_channel.py
imports: import os
  from .base_channel import BaseChannel
label_desc: Use image node_id 4 for calling the FileChannel obj's underlying member method code with example usage: obj._inner_send(message) without return types