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Solve the following problem using Python, implementing the functions described below, one line at a time
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<USER_TASK:>
Description:
 def update_user(self, user_id, **kwargs):
 """Update user properties of specified user. :param str user_id: The ID of the user to update (Required) :param str username: The unique username of the user :param str email: The unique email of the user :param str full_name: The full name of the user :param str password: The password string of the user. :param str phone_number: Phone number of the user :param bool terms_accepted: Is 'General Terms & Conditions' accepted :param bool marketing_accepted: Is receiving marketing information accepted? :returns: the updated user object :rtype: User """

        api = self._get_api(iam.AccountAdminApi)
        user = User._create_request_map(kwargs)
        body = iam.UserUpdateReq(**user)
        return User(api.update_user(user_id, body))