input: 
  from typing import List
  
  def remove_duplicates(numbers: List[int]) -> List[int]:
      """Removes all duplicate elements from a given list of integers.
      >>> remove_duplicates([1, 2, 3, 2, 4, 5, 6, 3])
      [1, 2, 3, 4, 5, 6]
      """
  
output:     seen = set()
      result = []
      for num in numbers:
          if num not in seen:
              seen.add(num)
              result.append(num)
      return result