* dependencies need to have a refcount to handle the case where they
* would be passed to more than one iterator. Upon iterator detroy, we
* iterate on all the gc ptrarray and decrement the refcounts, freeing
* if we reach 0.)
* (note to implementor: we calculate the dependency graph when
* dependencies need to have a refcount to handle the case where they
* would be passed to more than one iterator. Upon iterator detroy, we
* iterate on all the gc ptrarray and decrement the refcounts, freeing
* if we reach 0.)
* (note to implementor: we calculate the dependency graph when