input: Write a function that takes a list of integers and returns a new list containing only the even numbers from the original list. If the input list is empty, return an empty list.
  assert filter_even_numbers([1, 2, 3, 4, 5, 6])==[2, 4, 6]
  assert filter_even_numbers([7, 9, 11])==[]
  assert filter_even_numbers([2, 4, 6, 8])==[2, 4, 6, 8]
  assert filter_even_numbers([])==[]
output: def filter_even_numbers(lst):
      return [x for x in lst if x % 2 == 0]