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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 ffPDC(self):
 """Full frequency partial directed coherence. .. math:: \mathrm{ffPDC}_{ij}(f) = \\frac{A_{ij}(f)}{\sqrt{\sum_f A_{:j}'(f) A_{:j}(f)}} """

        A = self.A()
        return np.abs(A * self.nfft / np.sqrt(np.sum(A.conj() * A, axis=(0, 2),
                                                     keepdims=True)))