def METHOD_NAME():
    cache = LRUCache(maxsize=3)
    cache.set("key1", "value1")
    cache.set("key2", "value2")
    cache.set("key3", "value3")
    assert len(cache) == 3
    assert cache.get("key1") == "value1"
    cache.discard("key1")
    assert len(cache) == 2
    assert cache.get("key1") is None
    cache.discard("key4")  # key that does not exist
    assert len(cache) == 2  # size should not change