code: public void logBulk(Collection<String> messages, final Callback callback) {
          if (messages == null) return;
  
          String parcel = joinStrings(messages);
          if (parcel.isEmpty()) return;
  
          loggly.logBulk(token,
                  tags,
                  parcel,
                  new retrofit2.Callback<LogglyResponse>() {
                      @Override
                      public void onResponse(Call<LogglyResponse> call, Response<LogglyResponse> response) {
                          callback.success();
                      }
  
                      @Override
                      public void onFailure(Call<LogglyResponse> call, Throwable throwable) {
                          callback.failure(throwable.getMessage());
                      }
                  });
      }
docs: Posts several log messages in bulk to Loggly asynchronously
  @param messages messages to be logged
  @param callback callback to be invoked on completion of the post