class_docstr: generic multivariate Archimedean copula with additional power transforms
  
  Nelson p.144, equ. 4.5.2
  
  experimental, not yet tested and used
class_docstr_tok: ["generic","multivariate","Archimedean","copula","with","additional","power","transforms","Nelson","p.144",",","equ",".","4.5.2","experimental",",","not","yet","tested","and","used"]
code: def inverse(self, phi, alpha, beta, *tr_args):
      phi = np.asarray(phi)
      transf = self.transform
      phi_inv = np.power(
          transf.evaluate(np.power(phi, 1.0 / beta), *tr_args),
          1.0 / alpha,
      )
      return phi_inv
  
imports: import warnings
  import numpy
  from scipy.special import expm1, gamma
label_desc: Use image node_id 3 for calling the _TransfPower obj's underlying member method code with example usage: obj.inverse(phi, alpha, beta) and returns: phi_inv