input: Write a python function to remove duplicates from a list.
  assert remove_duplicates(['a','b','b','c','a','c'])==['a', 'b', 'c']
  assert remove_duplicates([1,2,2,3,4,4,5])==[1, 2, 3, 4, 5]
  assert remove_duplicates(['apple', 'banana', 'apple', 'orange'])==['apple', 'banana', 'orange']
output: def remove_duplicates(lst):
      return list(dict.fromkeys(lst))