input: Write a function to merge two sorted lists into a single sorted list. The function should take two lists as input and return a new list that is a merged and sorted combination of the two input lists.
  assert merge_sorted_lists([2,4,6], [3,5,7])==[2,3,4,5,6,7]
  assert merge_sorted_lists([1,3,5], [2,4,6])==[1,2,3,4,5,6]
  assert merge_sorted_lists([1], [2,3,4,5,6])==[1,2,3,4,5,6]
  assert merge_sorted_lists([], [2,3,4,5,6])==[2,3,4,5,6]
  assert merge_sorted_lists([], [])==[]
output: def merge_sorted_lists(list1, list2):
      result = []
      i, j = 0, 0
      while i < len(list1) and j < len(list2):
          if list1[i] < list2[j]:
              result.append(list1[i])
              i += 1
          else:
              result.append(list2[j])
              j += 1
      result.extend(list1[i:])
      result.extend(list2[j:])
      return result