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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 pauli_sum(*elements: Pauli) -> Pauli: """Return the sum of elements of the Pauli algebra"""

    terms = []

    key = itemgetter(0)
    for term, grp in groupby(heapq.merge(*elements, key=key), key=key):
        coeff = sum(g[1] for g in grp)
        if not isclose(coeff, 0.0):
            terms.append((term, coeff))

    return Pauli(tuple(terms))