Here's ChatGPT's take on it for what it's worth 😂:

Yes, the notation you're looking for is "top k argmax". It's a common notation used in machine learning and optimization.

Formally, if you have a function f(x) over a set X, the top k argmax of f(x) is the set of k elements in X that maximize f(x). The notation is usually written as:

argmax_{x\in X} f(x) = {x_1, x_2, ..., x_k}

where x_1, x_2, ..., x_k are the k elements in X that maximize f(x).

Note that if k=1, then the top k argmax reduces to the usual argmax notation.