[rules-users] Accumulate in Drools

[Manav]

Hi, 
I am trying my hand at the accumulate function in Drools 5.x but the drl fails 
to compile.
Not sure what's wrong with it. Please help.
This is the sample that i am working with 

rule "Test Accumulate Function"
when
 $p : ProductType ($name : name)
 $min_score : Number () 
   from accumulate (Client (productTypeExperience.keySet contains $name, 
                     $score : 
((ExperienceLevel)productTypeExperience[$name]).value()),
              min ($score)) 
then
 System.out.println ("$min_score" + $min_score);
end
Regards,
Manav