def fetch_seconds(other, base = nil)
      case other
      when ISO8601::Duration
        other.to_seconds(base)
      when Numeric
        other.to_f
      else
        raise(ISO8601::Errors::TypeError, other)
      end
    end
def fetch_seconds(other, base = nil)
      case other
      when ISO8601::Duration
        other.to_seconds(base)
      when Numeric
        other.to_f
      else
        raise(ISO8601::Errors::TypeError, other)
      end
    end
Fetch the number of seconds of another element.

 @param [ISO8601::Duration, Numeric] other Instance of a class to fetch
   seconds.

 @raise [ISO8601::Errors::TypeError] If other param is not an instance of
   ISO8601::Duration or Numeric classes

 @return [Float] Number of seconds of other param Object