def _SetListener(self, message_listener):
    'Internal method used by the protocol message implementation.\n    Clients should not call this directly.\n\n    Sets a listener that this message will call on certain state transitions.\n\n    The purpose of this method is to register back-edges from children to\n    parents at runtime, for the purpose of setting "has" bits and\n    byte-size-dirty bits in the parent and ancestor objects whenever a child or\n    descendant object is modified.\n\n    If the client wants to disconnect this Message from the object tree, she\n    explicitly sets callback to None.\n\n    If message_listener is None, unregisters any existing listener.  Otherwise,\n    message_listener must implement the MessageListener interface in\n    internal/message_listener.py, and we discard any listener registered\n    via a previous _SetListener() call.\n    '
    raise NotImplementedError
Internal method used by the protocol message implementation.
Clients should not call this directly.

Sets a listener that this message will call on certain state transitions.

The purpose of this method is to register back-edges from children to
parents at runtime, for the purpose of setting "has" bits and
byte-size-dirty bits in the parent and ancestor objects whenever a child or
descendant object is modified.

If the client wants to disconnect this Message from the object tree, she
explicitly sets callback to None.

If message_listener is None, unregisters any existing listener.  Otherwise,
message_listener must implement the MessageListener interface in
internal/message_listener.py, and we discard any listener registered
via a previous _SetListener() call.
def _SetListener(self, message_listener):
    'Internal method used by the protocol message implementation.\n    Clients should not call this directly.\n\n    Sets a listener that this message will call on certain state transitions.\n\n    The purpose of this method is to register back-edges from children to\n    parents at runtime, for the purpose of setting "has" bits and\n    byte-size-dirty bits in the parent and ancestor objects whenever a child or\n    descendant object is modified.\n\n    If the client wants to disconnect this Message from the object tree, she\n    explicitly sets callback to None.\n\n    If message_listener is None, unregisters any existing listener.  Otherwise,\n    message_listener must implement the MessageListener interface in\n    internal/message_listener.py, and we discard any listener registered\n    via a previous _SetListener() call.\n    '
    raise NotImplementedError