docs: def find_cfg_file(file_name=None):
      """Look for .netmiko.yml in current dir, then ~/.netmiko.yml."""
      base_file = ".netmiko.yml"
      check_files = [base_file, os.path.expanduser("~") + "/" + base_file]
      if file_name:
          check_files.insert(0, file_name)
      for test_file in check_files:
          if os.path.isfile(test_file):
              return test_file
      raise IOError("{}: file not found in current dir or home dir.".format(base_file))