How to use the constructs.Select function in constructs

assert(isinstance(expr, AbstractExpression))
    if (isinstance(expr, Value)):
        return expr.typ
    elif (isinstance(expr, constructs.Variable)):
        return expr.typ
    elif (isinstance(expr, constructs.Reference)):
        return expr.objectRef.typ
    elif (isinstance(expr, AbstractBinaryOpNode)):
        left_type = getType(expr.left)
        right_type = getType(expr.right)
        return result_type(left_type, right_type)
    elif (isinstance(expr, AbstractUnaryOpNode)):
        return getType(expr.child)
    elif (isinstance(expr, constructs.Cast)):
        return expr.typ
    elif (isinstance(expr, constructs.Select)):
        true_type = getType(expr.trueExpression)
        false_type = getType(expr.falseExpression)
        assert true_type == false_type
        return true_type
    elif (isinstance(expr, InbuiltFunction)):
        return expr.getType()
    raise TypeError(type(expr))

return simplify_expr(new_expr)
    elif (isinstance(expr, AbstractUnaryOpNode)):
        child = substitute_vars(expr.child, var_to_expr_map)
        op = expr.op
        new_expr = AbstractUnaryOpNode(child, op)
        return simplify_expr(new_expr)
    elif (isinstance(expr, constructs.Cast)):
        typ = expr.typ
        return \
            constructs.Cast(typ,
                            substitute_vars(expr.expression, var_to_expr_map))
    elif (isinstance(expr, constructs.Select)):
        new_cond = substitute_vars(expr.condition, var_to_expr_map)
        new_true = substitute_vars(expr.trueExpression, var_to_expr_map)
        new_false = substitute_vars(expr.falseExpression, var_to_expr_map)
        return constructs.Select(new_cond, new_true, new_false)
    elif (isinstance(expr, InbuiltFunction)):
        expr = expr.clone()
        expr.substitute_vars(var_to_expr_map)
        return expr
    raise TypeError(type(expr))