title: Calling a custom function in drools lhs
body: <p>I need to write a custom function that does some checks on the facts in drools working memory and returns a number.</p>
  
  <p>As far as I've figured out - I need to import the helper class which has the custom function. </p>
  
  <p>Now how to access the working memory from the function? And how would I call that function in the LHS?</p>