input: Write a function to remove all duplicate elements from a list and preserve the original order. The function name should be `remove_duplicates`, and it should take a list of integers as input. If the list is empty, it should 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([1, 1, 1, 1]) == [1]
  assert remove_duplicates([]) == []
  assert remove_duplicates([2, 4, 6, 4, 2, 8, 6, 10]) == [2, 4, 6, 8, 10]
output: def remove_duplicates(nums):
      new_list = []
      for num in nums:
          if num not in new_list:
              new_list.append(num)
      return new_list