pub trait CopyMat<T> {
// Required methods
fn copy_into(&self, dst: &Ref<DMatrix<T>>, offset: usize) -> usize;
fn copy_into_v(&self, dst: &Ref<DVector<T>>, offset: usize) -> usize;
fn copy_into_r(&self, dst: &Ref<RowDVector<T>>, offset: usize) -> usize;
fn copy_into_row_major(&self, dst: &Ref<DMatrix<T>>, offset: usize) -> usize;
}