In deep learning, a graph is represented as $G=(V,E)$, where $V=\{v_1,v_2,\dots,v_N\}$ is the set of nodes, and $E\subseteq V\times V$ is the set of edges between nodes. $N=|V|$ and $M=|E|$. $\mathbf{A}$ is the adjacency matrix of this graph.