Assigns some of the attributes of atoms in the PDB output file.
elbow.builder --smiles O --pdb_assign "chain B"
sets the chain to B.
Some of the attributes.
Residue name : resname
Chain ID : chain, chainid
Residue sequence ID : resseq, resid
Alternative location ID : altid, altloc
Insert code : icode
Occupancy : occ, occupancy
Temperature factor : tempfactor,