private boolean exists(DataType dt) {
		for (int i = 0; i < dataList.size(); i++) {
			DataType d = dataList.get(i);
			if (dt.isEquivalent(d)) {
				return true;
			}
		}
		return false;
	}
Return true if the given data type is the same type of any
data types in the list.
Ghidra/Framework/SoftwareModeling/src/main/java/ghidra/program/model/data/CycleGroup.java