input: Write a function to filter a list of integers and return only the even numbers. If the list is empty, return an empty list.
  assert filter_even_numbers([1, 2, 3, 4, 5, 6, 7, 8, 9, 10])==[2, 4, 6, 8, 10]
  assert filter_even_numbers([11, 13, 15, 17, 19])==[]
  assert filter_even_numbers([2, 4, 6, 8, 10])==[2, 4, 6, 8, 10]
  assert filter_even_numbers([])==[]
output: def filter_even_numbers(lst):
      return [x for x in lst if x % 2 == 0]