code: func Produces(args ...interface{}) {
  	if a, ok := apiDefinition(); ok {
  		if def := buildEncodingDefinition(true, args...); def != nil {
  			a.Produces = append(a.Produces, def)
  		}
  	}
  }
docs: // Produces can be used in: API
  //
  // Produces adds a MIME type to the list of MIME types the APIs can encode responses with.
  // Produces may also specify the path of the encoding package.
  // The package must expose a EncoderFactory method that returns an object which implements
  // goa.EncoderFactory.