[Lab 11] Suggested clarifications

[ehsan-ashik]

Going over the Lab 11 document, I felt that some of the aspects might be confusing to students and need further clarification.

1. The document does not clarify whether students are working with directed or undirected graph, which I felt is crucial and changes a lot.
2. There is potential for discrepancy which requires clarification. Please see some examples below -
   - When adding an edge, what should happen when one or both of the endpoints are not present in the vertices set? Should students add the vertex to the vertices list first and then add the edge - OR - should students raise an error?
   - When removing a vertex, whether the edges corresponding to the vertex should also be removed. If not, this can also cause discrepancy as an users can call the neighbors method on a vertex that was removed previously.