<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def _get_mu_tensor(self):
 """Get the min mu which minimize the surrogate. Returns: The mu_t. """

    root = self._get_cubic_root()
    dr = self._h_max / self._h_min
    mu = tf.maximum(
        root**2, ((tf.sqrt(dr) - 1) / (tf.sqrt(dr) + 1))**2)
    return mu