title: Drools Error : Unable to find @positional field
body: <p>I created a drool file PersonTotalAccountsBalance.drl as below. I am beginner in the rules engine world.</p>
  
  <pre><code>package com.auhuman.rules;
  
  import com.auhuman.Person;
  import com.auhuman.Account;
  
  function float getTotalBalance(Person person) {
       float totalBalance = 0;
       for (Account account : person.getAccounts()){
           totalBalance += account.getBalance();
       }
       return totalBalance;
  }
  
  rule "PersonTotalAccountsBalance"
      when
          $node : Person(active == true)
      then
          float totalBalance = getTotalBalance($node)
  
          modify($node) {
             setTotalBalance(totalBalance);
          }
  end
  </code></pre>
  
  <p>Upon compile I am getting below error</p>
  
  <pre><code>Unable to compile the file: PersonTotalAccountsBalance.drl. Errors = [Unable to find @positional field 0 for class Person
   : [Rule name='PersonTotalAccountsBalance']
  ]
  </code></pre>