    # File lib/fog/core/wait_for.rb, line 2
      def self.wait_for(timeout=Fog.timeout, interval=1, &block)
        duration = 0
        start = Time.now
        until yield || duration > timeout
          sleep(interval.to_f)
          duration = Time.now - start
        end
        if duration > timeout
          raise Errors::TimeoutError.new("The specified wait_for timeout (#{timeout} seconds) was exceeded")
        else
          { :duration => duration }
        end
      end