input: Write a python function to remove elements of one set from another.
  assert remove_elements({1, 2, 3, 4, 5}, {2, 4}) == {1, 3, 5}
  assert remove_elements({10, 20, 30}, {20, 30}) == {10}
  assert remove_elements({5, 6, 7, 8}, {1, 2, 3}) == {5, 6, 7, 8}
output: def remove_elements(set1, set2):
      return set1 - set2