def parents(self):
    'Returns the list of parent group indices for each group or C{None}\n        if the given group is the root.'
    return self._parent[:]
Returns the list of parent group indices for each group or C{None}
if the given group is the root.
def parents(self):
    'Returns the list of parent group indices for each group or C{None}\n        if the given group is the root.'
    return self._parent[:]