input: Write a function to remove all duplicates from a given list of numbers and return the new list with unique elements. If the given list is empty, return an empty list.
  assert deleteDuplicates([1, 2, 3, 2, 1])==[1, 2, 3]
  assert deleteDuplicates([5, 4, 5, 5, 6, 7])==[5, 4, 6, 7]
  assert deleteDuplicates([10, 10, 10, 10])==[10]
  assert deleteDuplicates([])==[]
output: def deleteDuplicates(nums):
      return list(dict.fromkeys(nums))