code: public <U> CoreRemoteMongoIterable<U> map(final Function<ResultT, U> mapper) {
      return new CoreRemoteMappingIterable<>(this, mapper);
    }
docs: Maps this iterable from the source document type to the target document type.
  
  @param mapper a function that maps from the source to the target document type
  @param <U> the target document type
  @return an iterable which maps T to U