Function GrB_Matrix_reduce_UDT 

pub unsafe extern "C" fn GrB_Matrix_reduce_UDT(
    c: *mut c_void,
    accum: GrB_BinaryOp,
    monoid: GrB_Monoid,
    A: GrB_Matrix,
    desc: GrB_Descriptor,
) -> GrB_Info