Function grab_region 

pub fn grab_region(
    tx: &mut Transaction<'_>,
    options: &GrabOptions,
    region: &[VertexId],
) -> Result<GrabReport>

grab over the candidates in region, with its cost following them instead of the mesh; see inflate_region for what region must hold. Grab needs no incidence index. A vertex no triangle uses moves only if it is listed.

Errors

As for grab.