input: Write a function to remove duplicates from a given list and return the list sorted in ascending order. The function should use a dictionary to remove duplicates and then convert it back to a sorted list.
  assert remove_duplicates([1, 2, 3, 4, 3, 2, 1])==[1, 2, 3, 4]
  assert remove_duplicates([10, 20, 30, 40, 30, 20, 10])==[10, 20, 30, 40]
  assert remove_duplicates(['a', 'b', 'c', 'b', 'a'])==['a', 'b', 'c']
  assert remove_duplicates([])==[]
  assert remove_duplicates([5])==[5]
output: def remove_duplicates(lst):
      return sorted(list(dict.fromkeys(lst)))