Add usage example for search_with_filtering

cpp/include/raft/neighbors/cagra.cuh

@@ -391,7 +391,25 @@ void search(raft::resources const& res,
 /**
  * @brief Search ANN using the constructed index with the given sample filter.
  *
- * See the [cagra::build](#cagra::build) documentation for a usage example.
+ * Usage example:
+ * @code{.cpp}
+ *   using namespace raft::neighbors;
+ *   // use default index parameters
+ *   cagra::index_params index_params;
+ *   // create and fill the index from a [N, D] dataset
+ *   auto index = cagra::build(res, index_params, dataset);
+ *   // use default search parameters
+ *   cagra::search_params search_params;
+ *   // create a bitset to filter the search
+ *   auto removed_indices = raft::make_device_vector<IdxT>(res, n_removed_indices);
+ *   raft::core::bitset<std::uint32_t, IdxT> removed_indices_bitset(
+ *     res, removed_indices.view(), dataset.extent(0));
+ *   // search K nearest neighbours according to a bitset
+ *   auto neighbors = raft::make_device_matrix<uint32_t>(res, n_queries, k);
+ *   auto distances = raft::make_device_matrix<float>(res, n_queries, k);
+ *   cagra::search_with_filtering(res, search_params, index, queries, neighbors, distances,
+ *     filtering::bitset_filter(removed_indices_bitset.view()));
+ * @endcode
  *
  * @tparam T data element type
  * @tparam IdxT type of the indices