hold_count(exp:PREDICATE[ANY,TUPLE[KEY,VAL]]) : INTEGER
local
    i,r:INTEGER
    t:TUPLE[KEY,VAL]
do
    t.make
    from
        i:=1
        r:=0
    until
        i>count
    loop
        t:=[keys[i],values[i]]
        if(exp.item(t)) then --alternative exp[keys[i],values[i]] didnt think of it someone told me so I don't know if it works
            r:= r+1
        end
    i:=i+1
    end
    Result:=r
end