@Override
	public int getNumParents() {
		lock.acquire();
		try {
			checkIsValid();
			Field[] keys =
				parentChildAdapter.getParentChildKeys(-key, ParentChildDBAdapter.CHILD_ID_COL);
			return keys.length;
		}
		catch (IOException e) {
			moduleMgr.dbError(e);
		}
		finally {
			lock.release();
		}
		return 0;
	}
Constructor
@param moduleMgr module manager
@param cache fragment DB cache
@param record fragment record
@param addrSet fragment address set
Ghidra/Framework/SoftwareModeling/src/main/java/ghidra/program/database/module/FragmentDB.java