`AddWithIDs` throws "add_with_ids not implemented for this type of index" with `IndexFactory`-created Flat index

[joy1990]

Title: AddWithIDs throws "add_with_ids not implemented for this type of index" with IndexFactory-created Flat index

Description: I'm trying to add vectors with custom IDs using AddWithIDs on an index created via IndexFactory with Flat type, but getting an error indicating the method isn't implemented for this index type.

Reproduction Steps:

package main

import "github.com/DataIntelligenceCrew/go-faiss"

func main() {
	test01()
}

func test01() {
	// Create Flat index via IndexFactory
	index, _ := faiss.IndexFactory(32, "Flat", faiss.MetricInnerProduct)

	// Add vector with custom ID
	vectors := [][]float32{
		{1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32},
	}
	err := index.AddWithIDs(vectors[0], []int64{22}) // <-- Error occurs here
	print(err)
}