She was grateful for everything that the medical and

nursing team had done for her. On her day of discharge, we shared in her delight

at her recovery. As she was leaving she was eager to say goodbye to each of us

in the nursing team. When she reached one nurse, she tried to press a

five-pound note into her hand. My colleague refused to accept it, saying that

we were all just doing our job. The patient looked puzzled, and then replied:

“Oh this isn’t for the care I had. I take that as a given. No, this is for setting my hair yesterday.”

上面的一段摘自2021全国卷Ⅰ（乙卷）完形填空题。请问其中的 given 是什么用法？

I take that as a given.

这里的 given 前面有不定冠词，说前它是名词吧？但查词典，given 用作名词时意思是“假设事实”“基本事实”“不争的事实”等，感觉用在上面的高考题句子中说不通吧！