code: func UserAgent(userAgent string) Option {
  	return func(api *API) error {
  		api.UserAgent = userAgent
  		return nil
  	}
  }
docs: // UserAgent can be set if you want to send a software name and version for HTTP access logs.
  // It is recommended to set it in order to help future Customer Support diagnostics
  // and prevent collateral damage by sharing generic User-Agent string with abusive users.
  // E.g. "my-software/1.2.3". By default generic Go User-Agent is used.