rulebook-core/src/main/java/com/deliveredtechnologies/rulebook/lang/RuleBookBuilder.java
public <U> RuleBookAddRuleBuilder<T> addRule(Rule<U, T> rule) {
    return new RuleBookAddRuleBuilder<>(newRuleBook(), rule);
  }
public <U> RuleBookAddRuleBuilder<T> addRule(Rule<U, T> rule) {
    return new RuleBookAddRuleBuilder<>(newRuleBook(), rule);
  }
Adds a rule to the RuleBook.
@param rule  Rule to be added into the RuleBook
@param <U>   the fact type of the Rule
@return      RuleBookBuilder with the added Rule