private static final Enum getEnum(long enumIndex, DataTypeManager dtm) {
		long dataTypeId =
			((long) DataTypeManagerDB.ENUM << DataTypeManagerDB.DATA_TYPE_KIND_SHIFT) | enumIndex;
		DataType dataType = dtm.getDataType(dataTypeId);
		if (!(dataType instanceof Enum)) {
			return null;
		}
		return (Enum) dataType;
	}
Get the Enum which corresponds to the specified enumIndex and the 
specified data type manager.
@param enumIndex enum data type index used by bit-field
@param dtm data type manager
@return Enum data type or null if not found
Ghidra/Framework/SoftwareModeling/src/main/java/ghidra/program/database/data/BitFieldDBDataType.java