input: 
  from typing import List
  
  def remove_duplicates(nums: List[int]) -> List[int]:
      """ Remove all duplicate elements from the given list while preserving the original order.
      >>> remove_duplicates([1, 3, 3, 5, 5, 7])
      [1, 3, 5, 7]
      >>> remove_duplicates([2, 2, 2, 2])
      [2]
      """
  
output:     seen = set()
      result = []
      for num in nums:
          if num not in seen:
              seen.add(num)
              result.append(num)
      return result