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