@Override
	public boolean canExpand() {
		FcgLevel level = vertex.getLevel();
		FcgDirection direction = level.getDirection();
		if (direction.isSource()) {
			return canExpandIncomingReferences() || canExpandOutgoingReferences();
		}

		if (direction.isIn()) {
			return canExpandIncomingReferences();
		}

		return canExpandOutgoingReferences();
	}
Returns true if this vertex can expand itself in its current direction, or in either
direction if this is a source vertex

@return true if this vertex can be expanded
Ghidra/Features/GraphFunctionCalls/src/main/java/functioncalls/graph/FcgVertexShapeProvider.java