7. Immediate edge selectors

7.1. igraph_ess_all — Edge set, all edges (immediate version)
7.2. igraph_ess_none — Immediate empty edge selector.
7.3. igraph_ess_1 — Immediate version of the single edge edge selector.
7.4. igraph_ess_vector — Immediate vector view edge selector.
7.5. igraph_ess_seq — Immediate version of the sequence edge selector.