Function trsv 

pub fn trsv<T: ComplexScalar>(
    op: Trans,
    alpha: T,
    a: &ComplexSparseMatrix<T>,
    descr: &MatDescr,
    b: &[T],
    x: &mut [T],
) -> Result<()>

Solve op(A) · x = α · b where A is sparse triangular.