code: private static RequestToken doCount(String collection, BaasQuery.Criteria filter, int flags, final BaasHandler<Long> handler) {
          BaasBox box = BaasBox.getDefaultChecked();
          filter = filter==null?BaasQuery.builder().count(true).criteria()
                               :filter.buildUpon().count(true).criteria();
          
          if (collection == null) throw new IllegalArgumentException("collection cannot be null");
  
          Count count = new Count(box, collection, filter, flags, handler);
          return box.submitAsync(count);
      }
docs: Asynchronously retrieves the number of documents readable to the user that match the <code>filter</code>
  in <code>collection</code>
  
  @param collection the collection to doCount not <code>null</code>
  @param filter     a {@link BaasQuery.Criteria} to apply to the request. May be <code>null</code>
  @param handler    a callback to be invoked with the result of the request
  @return a {@link com.baasbox.android.RequestToken} to handle the asynchronous request