io_data.hetatm -- whether to read HETATM records

If set to True, then all non-water 'HETATM' records are read from PDB or mmCIF files. (By default, only 'ATOM' records are read. To read waters, use io_data.water.) Note that you will usually need to turn this on when using BLK residues, or if you want to use a PDB or mmCIF file containing ligands.