code: func (api *API) parseOptions(opts ...Option) error {
  	// Range over each options function and apply it to our API type to
  	// configure it. Options functions are applied in order, with any
  	// conflicting options overriding earlier calls.
  	for _, option := range opts {
  		err := option(api)
  		if err != nil {
  			return err
  		}
  	}
  
  	return nil
  }
docs: // parseOptions parses the supplied options functions and returns a configured
  // *API instance.