input: Write a function to remove all duplicate elements from a list of integers. The function should return a new list with only unique elements.
  
  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]
  assert remove_duplicates([]) == []
output: def remove_duplicates(lst):
      return list(set(lst))