code: func (c *Client) Sizes() (uint32, uint32, uint32, uint32, error) {
  	return c.ctx.Sizes()
  }
docs: // Sizes queries the context for the sizes used in per-message functions.
  // It returns the maximum token size used in authentication exchanges, the
  // maximum signature size, the preferred integral size of messages, the
  // size of any security trailer, and any error.