doc: SCHWED-5901 bug in "ligand" label assignment by default.

modules/io/pymod/__init__.py

@@ -356,7 +356,10 @@ def LoadMMCIF(filename, fault_tolerant=None, calpha_only=None,
   customize the exact behaviour of the mmCIF import. For more information on
   these options, see :doc:`profile`.
   
-  Residues are flagged as ligand if they are mentioned in a HET record.
+  Residues are flagged as ligand if they are not covered by an ``entity_poly``
+  record (ie. they are non-polymer entities in ``pdbx_entity_nonpoly``). Note
+  that all residues will be flagged as ligands if ``seqres=False`` (the
+  default).
 
   :param filename: File to be loaded
   :type filename: :class:`str`