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Treehouse offers a seven day free trial for new students. Get access to thousands of hours of content and join thousands of Treehouse students and alumni in the community today.  # It works in workspace {python}

question: let's write some functions to explore set math a bit more. We're going to be using this COURSES dict in all of the examples. Don't change it, though!

So, first, write a function named covers that accepts a single parameter, a set of topics. Have the function return a list of courses from COURSES where the supplied set and the course's value (also a set) overlap.

For example, covers({"Python"}) would return ["Python Basics"].

When i try this in my workspace it totaly works so I do not understand why I get a bummer.

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(arg):
lista = []
if COURSES["Python Basics"].intersection(arg) == arg:
lista.append("Python Basics")
elif COURSES["Java Basics"].intersection(arg) == arg:
lista.append("Java Basics")
elif COURSES["PHP Basics"].intersection(arg) == arg:
lista.append("PHP Basics")
elif COURSES["Ruby Basics"].intersection(arg) == arg:
lista.append("Ruby Basics")
else:
lista.append("hoi")
return lista
```