input: Write a function to remove all duplicates from a given list of numbers. If the given list is empty then return an empty list.
  assert deleteDuplicates([1, 2, 2, 3, 3, 3])==[1, 2, 3]
  assert deleteDuplicates([4, 4, 5, 6, 5])==[4, 5, 6]
  assert deleteDuplicates([7, 8, 7, 8, 8])==[7, 8]
  assert deleteDuplicates([9, 9, 9, 9])==[9]
  assert deleteDuplicates([])==[]
output: def deleteDuplicates(nums):
      return list(dict.fromkeys(nums))