input: Write a python function to extract even numbers from a list of integers.
  assert ExtractEvens([1,2,3,4,5]) == [2,4]
  assert ExtractEvens([4,5,6,7,8,0,1]) == [4,6,8,0]
  assert ExtractEvens([8,12,15,19]) == [8,12]
output: def ExtractEvens(nums):
      return [num for num in nums if num % 2 == 0]