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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 _sumterm_prime(lexer):
 """Return a sum term' expression, eliminates left recursion."""

    tok = next(lexer)
    # '|' XORTERM SUMTERM'
    if isinstance(tok, OP_or):
        xorterm = _xorterm(lexer)
        sumterm_prime = _sumterm_prime(lexer)
        if sumterm_prime is None:
            return xorterm
        else:
            return ('or', xorterm, sumterm_prime)
    # null
    else:
        lexer.unpop_token(tok)
        return None