[IMP-dev] Anchoring part of a model

I would like to anchor a component of a complex while the others are optimized. With the MonteCarlo sampler is easy, just not adding a mover to the component. But ConjugateGradients moves the position anyway. Is there any way to nicely do this, or do I have to go to each particle of the component and set_is_optimized as False for all the x,y,z keys?