def extend_instance(obj, mixin):
    """Apply mixins to a class instance after creation"""
    base_cls = obj.__class__
    base_cls_name = obj.__class__.__name__
    obj.__class__ = type(
        base_cls_name, (mixin, base_cls), {}
    )  # mixin needs to go first for our forward() logic to work


def getattr_recursive(obj, att):
    """
    Return nested attribute of obj
    Example: getattr_recursive(obj, 'a.b.c') is equivalent to obj.a.b.c
    """
    if att == "":
        return obj
    i = att.find(".")
    if i < 0:
        return getattr(obj, att)
    else:
        return getattr_recursive(getattr(obj, att[:i]), att[i + 1 :])


def setattr_recursive(obj, att, val):
    """
    Set nested attribute of obj
    Example: setattr_recursive(obj, 'a.b.c', val) is equivalent to obj.a.b.c = val
    """
    if "." in att:
        obj = getattr_recursive(obj, ".".join(att.split(".")[:-1]))
    setattr(obj, att.split(".")[-1], val)


def _infer_decoder_layers_attr_name(model):
    for k in __KNOWN_DECODER_LAYERS_ATTR_NAMES:
        if k.lower() in model.__class__.__name__.lower():
            return __KNOWN_DECODER_LAYERS_ATTR_NAMES[k]

    raise ValueError(
        "We require the attribute name for the nn.ModuleList in the decoder storing"
        " the transformer block layers. Please supply this string manually."
    )


__KNOWN_DECODER_LAYERS_ATTR_NAMES = {
    "llama": "model.layers",
    "mistral": "model.layers",
}