input: from typing import List
  
  def removeDuplicates(array: List[int]) -> List[int]:
      """Remove duplicate elements from the given list of integers and return the list without duplicates.
      Use built-in functions to optimize the solution.
      >>> removeDuplicates([1, 2, 3, 2, 1])
      [1, 2, 3]
      >>> removeDuplicates([5, 5, 5, 5])
      [5]
      """
output:     return list(dict.fromkeys(array))