title: Incremental model update with PyMC3
body: <p>Is it possible to incrementally update a model in pyMC3. I can currently find no information on this. All documentation is always working with a priori known data.</p>
  
  <p>But in my understanding, a Bayesian model also means being able to update a belief. Is this possible in pyMC3? Where can I find info in this?</p>
  
  <p>Thank you :)</p>