def refresh_mrrt(responses, resource)
      logger.verbose("Attempting to obtain access token for #{resource} by " \
                     "refreshing 1 of #{responses.count(&:mrrt?)} matching " \
                     'MRRTs.')
      responses.each do |response|
        if response.mrrt?
          refresh_response = response.refresh(resource)
          return refresh_response if add(refresh_response)
        end
      end
      nil
    end
def refresh_mrrt(responses, resource)
      logger.verbose("Attempting to obtain access token for #{resource} by " \
                     "refreshing 1 of #{responses.count(&:mrrt?)} matching " \
                     'MRRTs.')
      responses.each do |response|
        if response.mrrt?
          refresh_response = response.refresh(resource)
          return refresh_response if add(refresh_response)
        end
      end
      nil
    end
Attempts to obtain an access token for a resource with refresh tokens from
 a list of MRRTs.

 @param Array[CachedTokenResponse]
 @return SuccessResponse|nil