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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 lf_polarities(L):
 """Return the polarities of each LF based on evidence in a label matrix. Args: L: an n x m scipy.sparse matrix where L_{i,j} is the label given by the jth LF to the ith candidate """

    polarities = [sorted(list(set(L[:, i].data))) for i in range(L.shape[1])]
    return [p[0] if len(p) == 1 else p for p in polarities]