def model_find_param_name(model, param_to_find):
    """Look up the name of a model parameter.

    Arguments:
        model: the model to search
        param_to_find: the parameter whose name we want to look up

    Returns:
        The parameter name (string) or None, if the parameter was not found.
    """
    for name, param  in model.named_parameters():
        if param is param_to_find:
            return name
    return None