something which is affirmed or denied concerning an argument of a proposition.

Here is what the above code is Doing:
1. It’s defining a function called ‘get_premises’ which takes two arguments: ‘proposition’ and ‘argument’.
2. It’s creating an empty list called ‘premises’.
3. It’s looping through every ‘premise’ in ‘proposition.premises’.
4. It’s appending every ‘premise’ to the ‘premises’ list.
5. It’s returning the ‘premises’ list.

So basically, the ‘get_premises’ function takes a ‘proposition’ and an ‘argument’ and returns a list of all the ‘premises’ in the ‘proposition’ which contain the ‘argument’.