def set_ext_params(ext_key, ext_params)
      raise ArgumentError unless ext_params.is_a?(Hash)
      @extensions[ext_key] = ext_params
    end
def set_ext_params(ext_key, ext_params)
      raise ArgumentError unless ext_params.is_a?(Hash)
      @extensions[ext_key] = ext_params
    end
Set the extension parameters for a specific vendor

 @param ext_key [String] The identifier for the vendor-specific parameters
 @param ext_params [Hash] The parameters, this is allowed to be two-levels deep