So, I am a complete beginner to recursion.

I have to answer a question in which I define a function that takes nested lists consisting of numbers or letters as parameters and I have to return a dictionary containing all the unique values. (I have to solve this problem recursivley) 

```
def extract_unique_elements(lists):
    if isinstance(lists, int):
        return {lists}

    for i in set(lists):
        return extract_unique_elements({i})

```

So obviously that isn't even close to working. If it were; however, when passed a nested list it would return as follows:

```
>>> extract_unique_elements([1,[2,1,[5,5,[2]]]]) 
{1,2,5}

>>> extract_unique_elements([a,[a,b,[c,b,[e]]]])
{a,b,c,e}

```