<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def exportable_keys(self):
 """Return a list of keys that are exportable from this tuple. Returns all keys that are not private in any of the tuples. """

    keys = collections.defaultdict(list)
    for tup in self._tuples:
      for key, private in tup._keys_and_privacy().items():
        keys[key].append(private)
    return [k for k, ps in keys.items() if not any(ps)]