* @return BitSet; or null if we mess up the type
	 */
	BitSet getAtomBits(String setType) {
		if (setType.equals("specialPosition"))
			return getSpecialPosition();
		if (setType.equals("symmetry"))
			return getSymmetrySet();
		if (setType.equals("unitcell"))
			return getUnitCellSet();
		if (setType.equals("hetero"))
			return getHeteroSet();
		if (setType.equals("hydrogen"))
			return getHydrogenSet();
		if (setType.equals("protein"))
			return getProteinSet();
		if (setType.equals("carbohydrate"))
			return getCarbohydrateSet();
		if (setType.equals("nucleic"))
			return getNucleicSet();
		if (setType.equals("dna"))
			return getDnaSet();
		if (setType.equals("rna"))
			return getRnaSet();
		if (setType.equals("purine"))
			return getPurineSet();
		if (setType.equals("pyrimidine"))
			return getPyrimidineSet();
		return null;
	}