input: Write a function to remove all duplicate elements from a list while preserving the original order. The function should return a new list with unique elements. The function should be named `remove_duplicates` and should take one parameter `nums` which is the list of numbers.
  assert remove_duplicates([1, 3, 3, 5, 5, 7])==[1, 3, 5, 7]
  assert remove_duplicates([2, 4, 4, 6, 8, 8])==[2, 4, 6, 8]
  assert remove_duplicates([1])==[1]
  assert remove_duplicates([])==[]
  assert remove_duplicates([5, 5, 5, 5])==[5]
output: def remove_duplicates(nums):
      seen = set()
      result = []
      for num in nums:
          if num not in seen:
              seen.add(num)
              result.append(num)
      return result