Double Key Priority Queue for Unity C#

PriorityQueue.cs

using System;
using System.Collections.Generic;
using UnityUtils;

public class PriorityQueue<T> {
    class KeyNodeComparer : IComparer<(Key, T)> {
        public int Compare((Key, T) x, (Key, T) y) {
            return x.Item1 < y.Item1 ? -1 : x.Item1 > y.Item1 ? 1 : 0;
        }
    }

    readonly SortedSet<(Key, T)> set = new(new KeyNodeComparer());
    readonly Dictionary<T, Key> lookups = new();

    public int Count => set.Count;
    public (Key, T) Min => set.Min;

    public void Add((Key, T) item) {
        set.Add(item);
        lookups[item.Item2] = item.Item1;
    }

    public void Remove(T item) {
        set.Remove((lookups[item], item));
        lookups.Remove(item);
    }

    public bool ContainsKey(T item) => lookups.ContainsKey(item);

    public bool Contains((Key, T) item) => set.Contains(item);

    public void Clear() => set.Clear();
}

public readonly struct Key {
    public readonly float k1;
    readonly float k2;

    public Key(float k1, float k2) {
        this.k1 = k1;
        this.k2 = k2;
    }

    public static bool operator <(Key a, Key b) => a.k1 < b.k1 || a.k1.Approx(b.k1) && a.k2 < b.k2;
    public static bool operator >(Key a, Key b) => a.k1 > b.k1 || a.k1.Approx(b.k1) && a.k2 > b.k2;
    public static bool operator ==(Key a, Key b) => a.k1.Approx(b.k1) && a.k2.Approx(b.k2);
    public static bool operator !=(Key a, Key b) => !(a == b);

    public override bool Equals(object obj) => obj is Key key && this == key;
    public override int GetHashCode() => HashCode.Combine(k1, k2);
    public override string ToString() => $"({k1}, {k2})";
}