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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 extract(self, inner_idx):
 """ Extracts a component of the underlying ProbabilityCurves, specified by the index `inner_idx`. """

        out = self.__class__(self.shape_y, 1)
        for sid in self:
            curve = self[sid]
            array = curve.array[:, inner_idx].reshape(-1, 1)
            out[sid] = ProbabilityCurve(array)
        return out