input: Write a function called `sum_even_numbers` that takes a list of integers as input and returns the sum of the even numbers in the list. If the input list is empty, return 0.
  
  assert sum_even_numbers([1, 2, 3, 4, 5, 6, 7, 8, 9, 10]) == 30
  assert sum_even_numbers([1, 3, 5, 7, 9]) == 0
  assert sum_even_numbers([2, 4, 6, 8, 10]) == 30
  assert sum_even_numbers([]) == 0
  assert sum_even_numbers([2, 2, 2]) == 6
output: def sum_even_numbers(lst):
      return sum(num for num in lst if num % 2 == 0)