RewindablePMMR

/// Rewindable (but still readonly) view of a PMMR.
pub struct RewindablePMMR<'a, T, B>
where
    T: PMMRable,
    B: 'a + Backend<T>,
{
    /// The last position in the PMMR
    last_pos: u64,
    /// The backend for this readonly PMMR
    backend: &'a B,
    // only needed to parameterise Backend
    _marker: marker::PhantomData<T>,
}