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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(lexer):
 """Return a sum term expresssion."""

    xorterm = _xorterm(lexer)
    sumterm_prime = _sumterm_prime(lexer)
    if sumterm_prime is None:
        return xorterm
    else:
        return ('or', xorterm, sumterm_prime)