'Return dictionaries describing the original binding levels.
This property returns a list of dictionaries describing each
original binding level if the port was previously bound, or
None if the port was unbound. The content is as described for
the binding_levels property.
This property is only valid within calls to
update_port_precommit and update_port_postcommit. It returns
None otherwise.'

@abc.abstractproperty
def original_binding_levels(self):

    pass
