input: Write a function to remove all duplicate elements from a list while preserving the original order. If the list is empty, return an empty list.
  def remove_duplicates(nums):
      new_list = []
      for num in nums:
          if num not in new_list:
              new_list.append(num)
      return new_list
  
  assert remove_duplicates([1, 3, 3, 5, 5, 7]) == [1, 3, 5, 7]
  assert remove_duplicates([3, 5, 2, 2, 5, 8, 3, 7]) == [3, 5, 2, 8, 7]
  assert remove_duplicates([10, 20, 30, 40, 20, 30]) == [10, 20, 30, 40]
  assert remove_duplicates([]) == []
output: def remove_duplicates(nums):
      new_list = []
      for num in nums:
          if num not in new_list:
              new_list.append(num)
      return new_list