code: public B setProviderNames(List<String> providers) {
          Objects.requireNonNull(providers);
          return set(AbstractQuery.KEY_QUERY_PROVIDERS, providers);
      }
docs: Set the providers to be considered. If not set explicitly the <i>default</i> ISO currencies as
  returned by {@link java.util.Currency} is used.
  
  @param providers the providers to use, not null.
  @return the query builder for chaining.