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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 is_null(*symbols):
 """ True if no nodes or all the given nodes are either None, NOP or empty blocks. For blocks this applies recursively """

    from symbols.symbol_ import Symbol

    for sym in symbols:
        if sym is None:
            continue
        if not isinstance(sym, Symbol):
            return False
        if sym.token == 'NOP':
            continue
        if sym.token == 'BLOCK':
            if not is_null(*sym.children):
                return False
            continue
        return False
    return True