code: func isAnsiCommandChar(b byte) bool {
  	switch {
  	case ansiterm.ANSI_COMMAND_FIRST <= b && b <= ansiterm.ANSI_COMMAND_LAST && b != ansiterm.ANSI_ESCAPE_SECONDARY:
  		return true
  	case b == ansiterm.ANSI_CMD_G1 || b == ansiterm.ANSI_CMD_OSC || b == ansiterm.ANSI_CMD_DECPAM || b == ansiterm.ANSI_CMD_DECPNM:
  		// non-CSI escape sequence terminator
  		return true
  	case b == ansiterm.ANSI_CMD_STR_TERM || b == ansiterm.ANSI_BEL:
  		// String escape sequence terminator
  		return true
  	}
  	return false
  }
docs: // isAnsiCommandChar returns true if the passed byte falls within the range of ANSI commands.
  // See http://manpages.ubuntu.com/manpages/intrepid/man4/console_codes.4.html.