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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def custom_arg(self, custom_arg):
 """Add custom args to the email :param value: A list of CustomArg objects or a dict of custom arg key/values :type value: CustomArg, list(CustomArg), dict """

        if isinstance(custom_arg, list):
            for c in custom_arg:
                self.add_custom_arg(c)
        else:
            self.add_custom_arg(custom_arg)