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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 get_v_total_stress_at_depth(self, z):
 """ Determine the vertical total stress at depth z, where z can be a number or an array of numbers. """


        if not hasattr(z, "__len__"):
            return self.one_vertical_total_stress(z)
        else:
            sigma_v_effs = []
            for value in z:
                sigma_v_effs.append(self.one_vertical_total_stress(value))
            return np.array(sigma_v_effs)