Function create_sparse_from_triplets_owned 

pub fn create_sparse_from_triplets_owned(
    triplets: Vec<(u64, u64, f32)>,
    mtx_shape: (usize, usize, usize),
    backend_file: Option<&str>,
    backend: Option<&SparseIoBackend>,
) -> Result<Box<dyn SparseIo<IndexIter = Vec<usize>>>>

Create a sparse backend from an owned triplet Vec.

Moves the Vec into the backend sort/write without copying. Use this on hot paths (e.g. from-* converters, merges) to avoid holding two full copies of the triplet list simultaneously.