input: Write a python function to merge two sorted lists.
  assert merge_sorted_lists([1, 3, 5, 7], [2, 4, 6, 8]) == [1, 2, 3, 4, 5, 6, 7, 8]
  assert merge_sorted_lists([10, 20, 30], [5, 15, 25, 35]) == [5, 10, 15, 20, 25, 30, 35]
  assert merge_sorted_lists([], [1, 2, 3]) == [1, 2, 3]
output: def merge_sorted_lists(list1, list2):
      merged_list = []
      i, j = 0, 0
      
      while i < len(list1) and j < len(list2):
          if list1[i] < list2[j]:
              merged_list.append(list1[i])
              i += 1
          else:
              merged_list.append(list2[j])
              j += 1
      
      while i < len(list1):
          merged_list.append(list1[i])
          i += 1
  
      while j < len(list2):
          merged_list.append(list2[j])
          j += 1
  
      return merged_list