input: Write a python function to combine two lists by alternating their elements, starting with the first list.
  assert combine_list([1, -2, 3], [4, 5, -6]) == [1, 4, -2, 5, 3, -6]
  assert combine_list([1, 2], [3, 4, 5, 6]) == [1, 3, 2, 4, 5, 6]
  assert combine_list([], [1, 2, 3]) == [1, 2, 3]
  assert combine_list([7, 8, 9], []) == [7, 8, 9]
output: def combine_list(list1, list2):
      combined = []
      len1, len2 = len(list1), len(list2)
      for i in range(max(len1, len2)):
          if i < len1:
              combined.append(list1[i])
          if i < len2:
              combined.append(list2[i])
      return combined