code: def deriv4_inverse(self, phi, theta):
      et = np.exp(theta)
      ept = np.exp(phi + theta)
      p = phi
      b = theta
      d4 = (
          (et - 1)
          * ept
          * (
              -4 * ept
              + np.exp(2 * (p + b))
              + 4 * np.exp(p + 2 * b)
              - 2 * et
              + np.exp(2 * b)
              + 1
          )
      ) / (b * (ept - et + 1) ** 4)
  
      return d4
  
imports: import warnings
  import numpy
  from scipy.special import expm1, gamma
label_desc: Use image node_id 7 for calling the TransfFrank obj's underlying member method code with example usage: obj.deriv4_inverse(phi, theta) and returns: d4