code: protected MultiMap resolveHeaders()
      {
          MultiMap resolved = null;
          if(headerFactory != null)
              resolved = headerFactory.getHeaders();
  
          if(resolved != null)
              resolved = resolved.merge(headers);
          else
              resolved = headers;
  
          return resolved;
      }
docs: Combine any locally defined headers with any headers from the header factory
  @return The headers to use for this request