def _auto_config(cla55: Type[T]) -> Config[T]:
    """
    Create the ``Config`` for a class by reflecting on its ``__init__``
    method and applying a few hacks.
    """
    typ3 = _get_config_type(cla55)

    # Don't include self, or vocab
    names_to_ignore = {"self", "vocab"}

    # Hack for RNNs
    if cla55 in [torch.nn.RNN, torch.nn.LSTM, torch.nn.GRU]:
        cla55 = torch.nn.RNNBase
        names_to_ignore.add("mode")

    if isinstance(cla55, type):
        # It's a class, so inspect its constructor
        function_to_inspect = cla55.__init__
    else:
        # It's a function, so inspect it, and ignore tensor
        function_to_inspect = cla55
        names_to_ignore.add("tensor")

    argspec = inspect.getfullargspec(function_to_inspect)
    comments = _docspec_comments(cla55)

    items: List[ConfigItem] = []

    num_args = len(argspec.args)
    defaults = list(argspec.defaults or [])
    num_default_args = len(defaults)
    num_non_default_args = num_args - num_default_args

    # Required args all come first, default args at the end.
    defaults = [_NO_DEFAULT for _ in range(num_non_default_args)] + defaults

    for name, default in zip(argspec.args, defaults):
        if name in names_to_ignore:
            continue
        annotation = argspec.annotations.get(name)
        comment = comments.get(name)

        # Don't include Model, the only place you'd specify that is top-level.
        if annotation == Model:
            continue

        # Don't include DataIterator, the only place you'd specify that is top-level.
        if annotation == DataIterator:
            continue

        # Don't include params for an Optimizer
        if torch.optim.Optimizer in getattr(cla55, '__bases__', ()) and name == "params":
            continue

        # Don't include datasets in the trainer
        if cla55 == Trainer and name.endswith("_dataset"):
            continue

        # Hack in our Optimizer class to the trainer
        if cla55 == Trainer and annotation == torch.optim.Optimizer:
            annotation = AllenNLPOptimizer

        # Hack in embedding num_embeddings as optional (it can be inferred from the pretrained file)
        if cla55 == Embedding and name == "num_embeddings":
            default = None

        items.append(ConfigItem(name, annotation, default, comment))

    # More hacks, Embedding
    if cla55 == Embedding:
        items.insert(1, ConfigItem("pretrained_file", str, None))

    return Config(items, typ3=typ3)