presto-hive/src/main/java/io/prestosql/plugin/hive/HiveTableProperties.java/HiveTableProperties/getSingleCharacterProperty
class HiveTableProperties:    public static Optional<Character> getSingleCharacterProperty(Map<String, Object> tableProperties, String key)
    {
        Object value = tableProperties.get(key);
        if (value == null) {
            return Optional.empty();
        }
        String stringValue = (String) value;
        if (stringValue.length() != 1) {
            throw new PrestoException(INVALID_TABLE_PROPERTY, format("%s must be a single character string, but was: '%s'", key, stringValue));
        }
        return Optional.of(stringValue.charAt(0));
    }