input: Write a function to delete all duplicates in a given list of numbers. If the input list is empty, return an empty list.
  assert deleteDuplicates([1, 2, 3, 4, 4, 5, 6, 6, 7])==[1, 2, 3, 4, 5, 6, 7]
  assert deleteDuplicates([10, 10, 20, 30, 40, 40])==[10, 20, 30, 40]
  assert deleteDuplicates([1, 1, 1, 1, 1])==[1]
  assert deleteDuplicates([])==[]
output: def deleteDuplicates(nums):
      return list(dict.fromkeys(nums))