Handle Models

[douweschulte]

If I open and save pTLS-6484.pdb (an ensemble crystallographic pdb file) it crashes Chimera, but the original file does not. So clearly there is something different in the output. Also it would be cool to know what has to be enforced in terms of Atom list equality between the models, right now it enforces that every model has the exact same Atoms (except different position etc) which is not true for the mentioned PDB file.

[douweschulte]

As of now Chimera and PyMol can both open the ensemble file, so I guess it was linked to #38. But the question remains how strict to be on validating of models, so do HETATMs also need to correspond to each other

[douweschulte]

Based on the file format definition (v3.30) also the HETATMs should correspond, but I have seen examples where this is not the case. So I would propose to issue a LooseWarning when finding HETATMs that do not correspond.

This record is used only when more than one model appears in an entry. Generally, it is
employed mainly for NMR structures. The chemical connectivity should be the same for each
model. ATOM, HETATM, ANISOU, and TER records for each model structure and are
interspersed as needed between MODEL and ENDMDL records.