input: Write a function to find the intersection of two sets of integers. The function should return a set containing elements that are present in both input sets.
  def intersection(set1, set2):
     return set1 & set2
  assert intersection({1, 2, 3, 4}, {3, 4, 5, 6})=={3, 4}
  assert intersection({5, 6, 7}, {7, 8, 9})=={7}
  assert intersection({1, 2, 3}, {4, 5, 6})==set()
  assert intersection(set(), {1, 2, 3})==set()
  assert intersection({1, 2, 3}, set())==set()
output: def intersection(set1, set2):
     return set1 & set2