def get_param(key, default=nil)
      key = expand_local_name(@node_name, key)
      param = @parameter.get_param(key)
      if param
        param
      else
        default
      end
    end
def get_param(key, default=nil)
      key = expand_local_name(@node_name, key)
      param = @parameter.get_param(key)
      if param
        param
      else
        default
      end
    end
get the param for key.
 You can set default value. That is uesed when the key is not set yet.
 @param [String] key key for search the parameters
 @param [String, Integer, Float, Boolean] default default value
 @return [String, Integer, Float, Boolean] parameter value for key