input: Write a function to remove all duplicate elements from a given list of integers and return the new list. If the input list is empty, return an empty list.
  assert remove_duplicates([1, 2, 3, 2, 4, 5, 6, 3])==[1, 2, 3, 4, 5, 6]
  assert remove_duplicates([5, 5, 5, 5, 5])==[5]
  assert remove_duplicates([1, 2, 3, 4, 5])==[1, 2, 3, 4, 5]
  assert remove_duplicates([])==[]
  assert remove_duplicates([1])==[1]
output: def remove_duplicates(lst):
      return list(dict.fromkeys(lst))