code: @Override
  	public Chain getChainByPDB(String authId, int modelnr)
  			throws StructureException{
  
  		Chain c = getPolyChainByPDB(authId, modelnr);
  
  		if (c==null ) {
  			throw new StructureException("Could not find chain with authId \"" + authId + "\"" + " for PDB id " + pdb_id + ", model "+modelnr);
  		}
  
  		return c;
  	}
docs: {@inheritDoc}