Can a Muslim supplicate for his deceased non-Muslim mother?

It is forbidden to seek forgiveness for polytheists, even if they are relatives, because Allah the Almighty says: "It is not for the Prophet and those who believe to ask forgiveness for polytheists, even if they were close relatives, after it has become clear to them that they are companions of Hellfire." The Prophet, peace and blessings be upon him, sought his Lord's permission to ask forgiveness for his mother, but he was not granted permission. As for Abraham's, peace be upon him, seeking forgiveness for his father, it was due to a promise he had made to him. But when it became clear to him that he was an enemy of Allah, he disassociated himself from him.