The classic GCN model employs both of the symmetric normalization and self-loop approach. Specifically, $\mathbf{h}_{u}^{(k)}=\sigma(\mathbf{W}^{(k)}\sum_{v\in \mathcal{N}(u)\cap\{u\}} \frac {\mathbf{h}_v}{\sqrt{|\mathcal{N}(u)\mathcal{N}(v)|}})$