def _shrink(v, gamma):
        """Soft-shrinkage of an array with parameter gamma.

        Parameters
        ----------

        v : array
            Array containing the values to be applied to the shrinkage operator

        gamma : float
            Shrinkage parameter.

        Returns
        -------

        v : array
            The same input array after the shrinkage operator was applied.
        """
        pos = v > gamma
        neg = v < -gamma
        v[pos] -= gamma
        v[neg] += gamma
        v[np.logical_and(~pos, ~neg)] = .0
        return v