def _exprcomp(node):
    """Return a unique Expression complement."""
    try:
        comp = _LITS[node.data()]
    except KeyError:
        comp = _LITS[node.data()] = Complement(node)
    return comp
def _exprcomp ( node ) : try : comp = _LITS [ node . data ( ) ] except KeyError : comp = _LITS [ node . data ( ) ] = Complement ( node ) return comp
Return a unique Expression complement.