code: public static Builder withConfig(String location) {
          try {
              return new Builder(PushConfiguration.read(location));
          }
          catch(IOException e){
              logger.log(Level.SEVERE, "Could not read config file", e);
              return null;
          }
      }
docs: Starts a {@link Builder} using an external config file
  
  @param location of the push configuration file
  @return a {@link Builder} instance