input: Write a function to filter a list of integers and return only even numbers. The function should take a list of integers as input and return a list containing only the even integers.
  assert filter_even_numbers([1, 2, 3, 4, 5, 6, 7, 8, 9, 10])==[2, 4, 6, 8, 10]
  assert filter_even_numbers([1, 3, 5, 7, 9])==[]
  assert filter_even_numbers([2, 4, 6, 8, 10])==[2, 4, 6, 8, 10]
  assert filter_even_numbers([1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12])==[2, 4, 6, 8, 10, 12]
  assert filter_even_numbers([])==[]
output: def filter_even_numbers(lst):
      return [num for num in lst if num % 2 == 0]