def METHOD_NAME(systems=None):
    n_atoms_max = None if systems is None else max([len(s) for s in systems])
    final_kwargs = {
        "n_atoms_max": n_atoms_max,
        "permutation": "none",
    }
    final_kwargs.update(kwargs)
    if (
        final_kwargs["permutation"] == "random"
        and final_kwargs.get("sigma") is None
    ):
        final_kwargs["sigma"] = 2
    return EwaldSumMatrix(**final_kwargs)