input: Write a python function to find common elements between two sets.
  assert common_elements({1, 2, 3, 4, 5, 6, 7}, {2, 4, 5, 6}) == {2, 4, 5, 6}
  assert common_elements({10, 20, 30}, {15, 20, 25, 30}) == {20, 30}
  assert common_elements({100, 200, 300}, {400, 500}) == set()
output: def common_elements(set1, set2):
      return set1.intersection(set2)