code: func isBatch(raw json.RawMessage) bool {
  	for _, c := range raw {
  		// skip insignificant whitespace (http://www.ietf.org/rfc/rfc4627.txt)
  		if c == 0x20 || c == 0x09 || c == 0x0a || c == 0x0d {
  			continue
  		}
  		return c == '['
  	}
  	return false
  }
docs: // isBatch returns true when the first non-whitespace characters is '['