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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 detunings_indices(Neu, Nl, xiu):
 r"""Get the indices of the transitions of all fields. They are returned in the form that is, one list of pairs of indices for each field. [[(1, 0)], [(2, 0), (3, 0)]] """

    pairs = []
    for l in range(Nl):
        ind = []
        for iu in range(Neu):
            for ju in range(iu):
                if xiu[l, iu, ju] == 1:
                    ind += [(iu, ju)]
        pairs += [ind]
    return pairs