How to filter out "_id" from mongodb C driver results -

i have been going through documentation , i'm still lost on how filter out _id results mongodb using c driver.
want functionality i'm not sure

db.collection.find({"test":"pass"},{_id: false}); 

how include projection in c?

cursor = mongoc_collection_find (collection, mongoc_query_none, 0, 0, 0, query, null, null); 

after bit of trial , error able add flags search query. else here format appending no id flag mongoc search.

bson_t *field = bson_new();

bson_append_int32(field,"_id", 0);

to search pattern like

cursor = mongoc_collection_find (collection, mongoc_query_none, 0, 0, 0, query, field, null);