_generateCredentials(grpcApi) {
    let certBuffer = null

    // Current settable value for testing. If allowed to be overridden via
    // configuration, this should be removed in place of setting
    // this._rootCerts from config via normal configuration precedence.
    const envTestCerts = process.env.NEWRELIC_GRPCCONNECTION_CA
    const rootCerts = this._rootCerts || envTestCerts
    if (rootCerts) {
      logger.debug('Infinite tracing root certificates found to attach to requests.')
      try {
        certBuffer = Buffer.from(rootCerts, 'utf-8')
      } catch (err) {
        logger.warn('Failed to create buffer from rootCerts, proceeding without.', err)
      }
    }

    // null/undefined ca treated same as calling createSsl()
    return grpcApi.credentials.createSsl(certBuffer)
  }
Creates the GRPC credentials needed

@param {object} grpcApi grpc lib
@returns {object} ssl credentials