code: private void applyHeaders(Invocation.Builder builder, Map<String, Object> headers)
      {
          if(headers != null)
          {
              for (Map.Entry<String, Object> e : headers.entrySet())
              {
                  builder.header(e.getKey(), e.getValue());
              }
          }
      }
docs: Add the given set of headers to the web target.
  @param builder The invocation to add the headers to
  @param headers The headers to add