async def METHOD_NAME(pathname: str, content_type: str=''):
  """Add a local file. Note: this method will block the thread."""
  with open(pathname, 'rb') as file_object:
    grid_in = await add(content_type or mimetypes.guess_type(pathname)[0])
    await grid_in.write(file_object)
    await grid_in.close()
    return grid_in._id