<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def iterate_nodes(self, key, distinct=True):
 """hash_ring compatibility implementation. Given a string key it returns the nodes as a generator that can hold the key. The generator iterates one time through the ring starting at the correct position. if `distinct` is set, then the nodes returned will be unique, i.e. no virtual copies will be returned. """

        if not self.runtime._ring:
            yield None
        else:
            for node in self.range(key, unique=distinct):
                yield node['nodename']