def METHOD_NAME(self) -> str:
    """By the assumption that the node.built_value is a
    deterministic product of the sources, the contents of a Value
    are the concatenation of all the contents of its sources.  As
    the value need not be built when get_contents() is called, we
    cannot use the actual node.built_value."""
    ###TODO: something reasonable about universal newlines
    contents = str(self.value)
    for kid in self.children(None):
        # Get csig() value of child as this is more efficent
        contents = contents + kid.get_csig()
    return contents