public static String parse(String timeZone) {

        // Return null if no time zone provided
        if (timeZone == null || timeZone.isEmpty())
            return null;

        // Otherwise, assume time zone is valid
        return timeZone;

    }
Parses the given string into a time zone ID string. As these strings are
equivalent, the only transformation currently performed by this function
is to ensure that a blank time zone string is parsed into null.

@param timeZone
    The time zone string to parse, which may be null.

@return
    The ID of the time zone corresponding to the given string, or null
    if the given time zone string was null or blank.
guacamole-ext/src/main/java/org/apache/guacamole/form/TimeZoneField.java