Go read the instructions and get a better idea of what the purpose of your function is. Then think about what actions would help accomplishing that purpose.
I do not know what you think you mean by putting median inside is_median. But if you think it is something that would help in what your function is supposed to do - then motivate why it would be helpful. Or if you can't motivate it, then ask yourself where that thought is coming from.
For example, if I want to get some piece of soil wet, then filling up a watering can would be a sensible action if the watering can is of a size that I can carry and can hold sufficient amounts of water to wet the soil.
I wouldn't ask "am I supposed to fill a watering can" - because that isn't part of the purpose. If I've seen Fred the farmer use a watering can to wet soil, then that would be where that thought is coming from, and even though I don't see how it helps, I can go ask Fred.
So no, you're not supposed to put median in is_median, you're supposed to test median. If putting median in is_median helps you do that, then yes, it would be a sensible thing to do.
But again, I have no clue what you mean by that, and you very likely will need to think harder yourself about what you mean by it - or at least choose different words in describing that action.