static ExpressionConverter<Oql> converter(boolean useBindVariables, PathNaming pathNaming) {
    return expression -> expression.accept(new GeodeQueryVisitor(useBindVariables, pathNaming));
  }
Returns only predicate part to be appended to {@code WHERE} clause.

@return predicate, empty string if no predicate
criteria/geode/src/org/immutables/criteria/geode/Geodes.java