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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def save_external_nodes(sender, **kwargs):
 """ sync by creating nodes in external layers when needed """

    node = kwargs['instance']
    operation = 'add' if kwargs['created'] is True else 'change'

    if node.layer.is_external is False or not hasattr(node.layer, 'external') or node.layer.external.synchronizer_path is None:
        return False

    push_changes_to_external_layers.delay(node=node, external_layer=node.layer.external, operation=operation)