input: Write a function to remove all duplicate elements from a given list while preserving the original order.
  
  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([7, 7, 3, 9, 9, 5])==[7, 3, 9, 5]
  assert remove_duplicates([])==[]
  assert remove_duplicates([2, 2, 2, 2])==[2]
output: def remove_duplicates(nums):
      new_list = []
      for num in nums:
          if num not in new_list:
              new_list.append(num)
      return new_list