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# I'm very lost on the collections set math problem.

I've read through the teacher documents and other peoples questions and I still dont understand what to do here... I know im supposed to use the set math operators but i don't know where and I dont know how to loop and get the key without using 'if topic in' statement. i feel like the iter operator would be useful but i dont understand where I would put it

sets.py
```COURSES = {
"Python Basics": {"Python", "functions", "variables",
"booleans", "integers", "floats",
"arrays", "strings", "exceptions",
"conditions", "input", "loops"},
"Java Basics": {"Java", "strings", "variables",
"input", "exceptions", "integers",
"booleans", "loops"},
"PHP Basics": {"PHP", "variables", "conditions",
"integers", "floats", "strings",
"booleans", "HTML"},
"Ruby Basics": {"Ruby", "strings", "floats",
"integers", "conditions",
"functions", "input"}
}

def covers(topics):
keys=COURSES.keys()
values=COURSES.values()
key_set=[]
for keys in COURSES:
if topics in values:
key_set.append(keys)
return key_set
```

Remember that in for loops, best practice is for your first variable should be unique (relative to that particular for loop). You are trying to define it beforehand which is not as helpful. To achieve what I think you are aiming for, you could simply change the for loop to

```for key in keys
```

If we remember DRY, since you do not use your keys variable anywhere else in your function, you can simplify your code by removing

```keys=COURSES.keys()
```

and further change your for loop to

```for key in COURSES.keys()
```

Although, you are now looping through only the keys of each pair in the dict. You may want to rethink what you are looping through using the above logic.