Is this suppose to be `d_dp` or `_d_dp`? Does `InstanceBackedModel` implement `DP`? It doesn't look like it... Therefore I think if we want to put this here this should be `_d_dp`.

On the other hand the method here feels a bit strange, since all the other methods of this class are simple calls to `LinearModel` (or `PCAModel`) methods than transform the output to the particular `instance` representation of the original samples.

I believe `_d_dp` properties should be in `PCAModel` or `LinearModel`