How to use the pymoca.ast.Primary function in pymoca

delay_argument = DelayArgument(expr, duration)
            self.model.delay_arguments.append(delay_argument)
        elif op == '_pymoca_interp1d' and n_operands >= 3 and n_operands <= 4:
            entered_class = self.entered_classes[-1]
            if isinstance(tree.operands[0], ast.ComponentRef):
                xp = self.get_mx(entered_class.symbols[tree.operands[0].name].value)
            else:
                xp = self.get_mx(tree.operands[0])
            if isinstance(tree.operands[1], ast.ComponentRef):
                yp = self.get_mx(entered_class.symbols[tree.operands[1].name].value)
            else:
                yp = self.get_mx(tree.operands[1])
            arg = self.get_mx(tree.operands[2])
            if n_operands == 4:
                assert isinstance(tree.operands[3], ast.Primary)
                mode = tree.operands[3].value
            else:
                mode = 'linear'
            func = ca.interpolant('interpolant', mode, [xp], yp)
            src = func(arg)
        elif op == '_pymoca_interp2d' and n_operands >= 5 and n_operands <= 6:
            entered_class = self.entered_classes[-1]
            if isinstance(tree.operands[0], ast.ComponentRef):
                xp = self.get_mx(entered_class.symbols[tree.operands[0].name].value)
            else:
                xp = self.get_mx(tree.operands[0])
            if isinstance(tree.operands[1], ast.ComponentRef):
                yp = self.get_mx(entered_class.symbols[tree.operands[1].name].value)
            else:
                yp = self.get_mx(tree.operands[1])
            if isinstance(tree.operands[2], ast.ComponentRef):