input: Write a python function to filter out non-integer elements from a list.
  assert filter_integers([1, 'a', 2, 'b', 3, 4.5, 'c']) == [1, 2, 3]
  assert filter_integers(['x', 'y', 10, 'z', 20, 30.1]) == [10, 20]
  assert filter_integers([100, 200, 'hello', 300, 'world']) == [100, 200, 300]
output: def filter_integers(lst):
      return [x for x in lst if isinstance(x, int)]