code: def check_oneof(**kwargs):
      
      # Sanity check: If no keyword arguments were sent, this is fine.
      if not kwargs:
          return None
  
      not_nones = [val for val in kwargs.values() if val is not None]
      if len(not_nones) > 1:
          raise ValueError('Only one of {fields} should be set.'.format(
              fields=', '.join(sorted(kwargs.keys())),
          ))
docs: Raise ValueError if more than one keyword argument is not none.
  
      Args:
          kwargs (dict): The keyword arguments sent to the function.
  
      Returns: None
  
      Raises:
          ValueError: If more than one entry in kwargs is not none.