code: def inverse(self, phi, theta):
      phi = np.asarray(phi)
      return -np.log1p(np.exp(-phi) * expm1(-theta)) / theta
  
imports: import warnings
  import numpy
  from scipy.special import expm1, gamma
label_desc: Use image node_id 2 for calling the TransfFrank obj's underlying member method code with example usage: obj.inverse(phi, theta) and returns: unknown