code: function reduceSourceWithRule(source, rule, condition) {
    if (rule) {
      if (condition && source.condition !== condition) {
        // if source rules condition different from rule condition
        // update source condition
  
        source = {
          condition: condition,
          // if has more then one rules
          // regroup source rules tree
          rules: source.rules.length > 1 ? [source] : source.rules
        };
      }
  
      // add new rule
      source.rules.push(rule);
    }
    return source;
  }
docs: Reduce source with new rule and/or condition
  @param {Object} source - Source rule
  @param {Object|string} rule - Rule to add
  @param {string} [condition] - Condition for rule to add(and/or)
  @returns {Object} updated rule
  @private