def flatten_dict(config):
  """Flatten a hierarchical dict to a simple dict."""
  new_dict = {}
  for key, value in config.items():
    if isinstance(value, dict):
      sub_dict = flatten_dict(value)
      for subkey, subvalue in sub_dict.items():
        new_dict[key + "/" + subkey] = subvalue
    elif isinstance(value, tuple):
      new_dict[key] = str(value)
    else:
      new_dict[key] = value
  return new_dict