code: def arg_to_json(arg):
      
      conversion = json_conversions.get(type(arg))
      if conversion:
          return conversion(arg)
      for type_ in subclass_conversions:
          if isinstance(arg, type_):
              return json_conversions[type_](arg)
      return json_conversions[str](arg)
docs: Perform necessary JSON conversion on the arg.