input: Write a function that removes all duplicates from a given list and returns the list sorted in ascending order. The function should maintain the order of the first occurrence of each element from the input list. If the input list is empty, the function should return an empty list.
  
  assert remove_duplicates([3, 4, 5, 1, 2, 3, 4]) == [1, 2, 3, 4, 5]
  assert remove_duplicates([4, 3, 5, 4, 3, 2, 1]) == [1, 2, 3, 4, 5]
  assert remove_duplicates([1, 2, 3, 4, 3, 2, 1]) == [1, 2, 3, 4]
  assert remove_duplicates([]) == []
output: def remove_duplicates(lst):
      seen = set()
      result = []
      for item in lst:
          if item not in seen:
              seen.add(item)
              result.append(item)
      return sorted(result)