Function save_index 

pub fn save_index<T: Serialize, P: AsRef<Path>>(
    index: &T,
    path: P,
) -> Result<()>

Save an index to a JSON file

The index must implement Serialize. This works with all index types:

• VectorSearchIndex
• HnswIndex
• IvfPqIndex
• HybridIndex
• ColbertIndex