input: Write a function to remove all duplicates from a given list of numbers and return the new list with unique elements.
  assert deleteDuplicates([1, 2, 3, 2, 1])==[1, 2, 3]
  assert deleteDuplicates([4, 4, 4, 1, 2, 3, 1])==[4, 1, 2, 3]
  assert deleteDuplicates([5, 6, 7, 7, 8, 8, 9, 5])==[5, 6, 7, 8, 9]
  assert deleteDuplicates([])==[]
output: def deleteDuplicates(nums):
      return list(dict.fromkeys(nums))