private static int getTokenIndex(final List<AbstractToken> tokens, final Predicate<AbstractToken> predicate) {
        for (int i = 0; i < tokens.size(); i++) {
            final AbstractToken token = tokens.get(i);
            if (predicate.test(token)) {
                return i;
            }
        }
        return -1;
    }
@param isLenient Ignores any additional child tokens found. This is to support getting just
                 the data source from a partially written query, which is likely to not be
                 a valid query. For example, you may type
                 <pre>{@code from View sel}</pre> and at this point do code completion on 'sel'
                 so if this method is called it will treat 'sel as an extra child.
stroom-query/stroom-query-common/src/main/java/stroom/query/language/SearchRequestFactory.java