code: def dedupe_list(l):
      
      result = []
  
      for el in l:
          if el not in result:
              result.append(el)
  
      return result
docs: Remove duplicates from a list preserving the order.
  
      We might be tempted to use the list(set(l)) idiom, but it doesn't preserve
      the order, which hinders testability and does not work for lists with
      unhashable elements.