code: public static String combineFilters(String filterA, String operator, String filterB) {
          return String.format("(%s) %s (%s)", filterA, operator, filterB);
      }
docs: Creates a filter condition using the specified logical operator on two filter conditions.
  
  @param filterA
  A <code>String</code> which specifies the first formatted filter condition.
  @param operator
  A <code>String</code> which specifies <code>Operators.AND</code> or <code>Operators.OR</code>.
  @param filterB
  A <code>String</code> which specifies the first formatted filter condition.
  @return
  A <code>String</code> which represents the combined filter expression.