private void handleAttribute(String attribute, String value) {
        int pos = value.indexOf(':');
        if (pos != -1) {
            parseBitmap(attribute, value.substring(0, pos), value.substring(pos + 1));
        } else {
            addAttribute(attribute, value);
        }
    }
Handles one attribute, possibly with a subquery bitmap.
@param attribute Attribute name
@param value Either value, or value:bitmap, where bitmap is either a 64-bit hex number or a list of bits.
container-search/src/main/java/com/yahoo/search/querytransform/BooleanAttributeParser.java