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