2.1. igraph_independent_vertex_sets — Find all independent vertex sets in a graph

2.1. `igraph_independent_vertex_sets` — Find all independent vertex sets in a graph

int igraph_independent_vertex_sets(const igraph_t *graph,
				   igraph_vector_ptr_t *res,
				   igraph_integer_t min_size,
				   igraph_integer_t max_size);

A vertex set is considered independent if there are no edges between them.

If you are interested in the size of the largest independent vertex set, use igraph_independence_number() instead.

Arguments:

`graph`:	The input graph.
`res`:	Pointer to a pointer vector, the result will be stored here, ie. `res` will contain pointers to `igraph_vector_t` objects which contain the indices of vertices involved in an independent vertex set. The pointer vector will be resized if needed but note that the objects in the pointer vector will not be freed.
`min_size`:	Integer giving the minimum size of the sets to be returned. If negative or zero, no lower bound will be used.
`max_size`:	Integer giving the maximum size of the sets to be returned. If negative or zero, no upper bound will be used.

Returns:

Error code.

Time complexity: TODO