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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 get_itemtypesinsertion(cls, itemgroup, indent) -> str: """Return a string defining the required types for the given exchange item group. <complexType name="arma_v1_setitemsType"> </complexType> <BLANKLINE> <complexType name="dam_v001_setitemsType"> <complexType name="nodes_setitemsType"> """

        subs = []
        for modelname in cls.get_modelnames():
            subs.append(cls.get_itemtypeinsertion(itemgroup, modelname, indent))
        subs.append(cls.get_nodesitemtypeinsertion(itemgroup, indent))
        return '\n'.join(subs)