code: public static String normalize(Object expression) {
          if (expression == null) {
              return null;
          }
  
          // If it's a number it's not an expression
          if (expression instanceof Number){
              return String.valueOf(expression);
          }
  
          String replacement;
          String conditionStr = StringUtils.mergeToSingleUnderscore(String.valueOf(expression));
          Matcher matcher = PATTERN.matcher(conditionStr);
          StringBuffer result = new StringBuffer(conditionStr.length());
          while (matcher.find()) {
              if (OPERATORS.containsKey(matcher.group())) {
                  replacement = (String) OPERATORS.get(matcher.group());
              } else if (PREDEFINED_VARS.containsKey(matcher.group())) {
                  replacement = (String) PREDEFINED_VARS.get(matcher.group());
              } else {
                  replacement = matcher.group();
              }
              matcher.appendReplacement(result, replacement);
          }
          matcher.appendTail(result);
          return result.toString();
      }
docs: Normalize an expression string, replace "nice names" with their coded values and spaces with "_".
  
  @param expression an expression
  @return a parsed expression