code: func WithData(d []byte) source.Option {
  	return func(o *source.Options) {
  		if o.Context == nil {
  			o.Context = context.Background()
  		}
  		o.Context = context.WithValue(o.Context, changeSetKey{}, &source.ChangeSet{
  			Data:   d,
  			Format: "json",
  		})
  	}
  }
docs: // WithData allows the source data to be set