where t is the iteration step counter in message passing, W 2 is a learned weight matrix, and {V |N (i)\j} refers to the set of neighboring vertices or atoms connected to the i th atom, excluding the j th atom. After all message passing steps, the learned edge hidden information (h h h β,ij = h h h T β,ij , a.k.a. learned bond representation) is further converted to the learned atomic embedding, h h h α,i , by concatenating the sum of all the incoming bond features with the original vertex features: