code: def traverse_dependency_graph(self, ref, collector, memo=None):
      
  
      resolved_ref = self.refs_by_unversioned_refs.get(ref.unversioned)
      if resolved_ref:
        ref = resolved_ref
      if memo is None:
        memo = dict()
      visited = set()
      return self._do_traverse_dependency_graph(ref, collector, memo, visited)
docs: Traverses module graph, starting with ref, collecting values for each ref into the sets
      created by the collector function.
  
      :param ref an IvyModuleRef to start traversing the ivy dependency graph
      :param collector a function that takes a ref and returns a new set of values to collect for
             that ref, which will also be updated with all the dependencies accumulated values
      :param memo is a dict of ref -> set that memoizes the results of each node in the graph.
             If provided, allows for retaining cache across calls.
      :returns the accumulated set for ref