input: Write a function to find the intersection of two sets.
  assert intersection({1, 2, 3}, {3, 4, 5}) == {3}
  assert intersection({10, 20, 30}, {30, 40, 50}) == {30}
  assert intersection({'apple', 'banana'}, {'banana', 'cherry'}) == {'banana'}
output: def intersection(set1, set2):
      return set1 & set2