Please explain properly.

Give an example of a directed graph G = (V, E), a source vertex s elementof V, and a set of tree edges E_pi subsetoforequalto E such that for each vertex nu elementof V, the unique simple path in the graph (V, E_pi) from s to nu is a shortest path in G, yet the set of edges E_pi cannot be produced by running BFS on G, no matter how the vertices are ordered in each adjacency list