@Override
	public DataType toDataType() throws DuplicateNameException, IOException {
		StructureDataType structure = getBaseStructure("ModuleMainClass_attribute");
		structure.add(WORD, "main_class_index", null);
		return structure;
	}
{@code main_class index} must be a valid index into the constant pool. The entry at
that index must be a {@link ConstantPoolClassInfo} structure representing the main
class of the current module.
@return index of main class.
Ghidra/Processors/JVM/src/main/java/ghidra/javaclass/format/attributes/ModuleMainClassAttribute.java