Hello All,<br><br>It looks like there is a problem with the current stable version of yt that comes up when creating a PlotCollection using Orion datasets. See the script <a href="http://paste.yt-project.org/show/t02maMs6OShv1uGJbOLu/">here</a> and the traceback <a href="http://paste.yt-project.org/show/zAgcYyrKH2vmv4ZaQJQ5/">here.  </a><br>
<br>I think the fix is that there needs to be the line<br><br><div style="margin-left:40px">self.field_info = pf.field_info<br><br></div>somewhere in the constructor for OrionHierarchy (around line 120 of yt/frontends/orion/data_structures.py). It looks like a line like this used to be here, but was removed during some code cleanup. If the other Orion users are anything like me, they haven&#39;t updated yt in a while and thus haven&#39;t noticed the problem.<br>
<br>Glancing at the Nyx, Maestro, and Castro frontends, those look like they might suffer from the same issue, but I don&#39;t have any of their data to confirm or deny this.<br><br>-Andrew Myers <br>